Develop Reference

How do I install pip for python 3.8 on Ubuntu without changing any defaults?

I'm trying to install pip for Python 3.8 on an Ubuntu 18.04 LTS.
I know this has been asked way too many times. But those questions do not concern keeping Ubuntu's defaults specifically. And the answers on those questions either don't work or go on to suggest something so drastic that it would break the system - e.g. change default python3 version from 3.6 to 3.8. You SHOULDN'T!
So far, I've been able to install python3.8 successfully using the PPA - ppa:deadsnakes/ppa:
sudo add-apt-repository ppa:deadsnakes/ppa
sudo apt update
sudo apt install python3.8
Changed python command from python2 to python3.8 using update-alternatives:
update-alternatives --remove python /usr/bin/python2
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.8 10
Now, I get python 3.8 when I run python --version:
Python 3.8.5
The problem is, I still can't install pip for Python 3.8.
If I try to install python3-pip, it installs pip for Python 3.6 since python3 still points to python3.6.9, and I intend to keep it that way.
Try installing python-pip, and it will install pip for Python 2.7.
Also there's no such package as python3.8-pip, so I can't install it like:
sudo apt install python3.8-pip
Output:
E: Unable to locate package python3.8-pip
E: Couldn't find any package by glob 'python3.8-pip'
E: Couldn't find any package by regex 'python3.8-pip'
What can I do to install pip for Python 3.8 on an Ubuntu 18.04?

While we can use pip directly as a Python module (the recommended way):
python -m pip --version
This is how I installed it (so it can be called directly):
Firstly, make sure that command pip is available and it isn't being used by pip for Python 2.7
sudo apt remove python-pip
Now if you write pip in the Terminal, you'll get that nothing is installed there:
pip --version
Output:
Command 'pip' not found, but can be installed with:
sudo apt install python-pip
Install python3.8 and setup up correct version on python command using update-alternatives (as done in the question).
Make sure, you have python3-pip installed:
(This won't work without python3-pip. Although this will install pip 9.0.1 from python 3.6, we'll need it.)
sudo apt install python3-pip
This will install pip 9.0.1 as pip3:
pip3 --version
Output:
pip 9.0.1 from /usr/lib/python3/dist-packages (python 3.6)
Now, to install pip for Python 3.8, I used pip by calling it as a python module (ironic!):
python -m pip install pip
Output:
Collecting pip
  Downloading https://files.pythonhosted.org/packages/36/74/38c2410d688ac7b48afa07d413674afc1f903c1c1f854de51dc8eb2367a5/pip-20.2-py2.py3-none-any.whl (1.5MB)
  100% |████████████████████████████████| 1.5MB 288kB/s
Installing collected packages: pip
Successfully installed pip-20.2
It looks like, when I called pip (which was installed for Python 3.6, BTW) as a module of Python 3.8, and installed pip, it actually worked.
Now, make sure your ~/.local/bin directory is set in PATH environment variable:
Open ~/.bashrc using your favourite editor (if you're using zsh, replace .bashrc with .zshrc)
nano ~/.bashrc
And paste the following at the end of the file
# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/.local/bin" ] ; then
PATH="$HOME/.local/bin:$PATH"
fi
Finally, source your .bashrc (or restart the Terminal window):
source ~/.bashrc
Now if you try running pip directly it'll give you the correct version:
pip --version
Output:
pip 20.2 from /home/qumber/.local/lib/python3.8/site-packages/pip (python 3.8)
Sweet!

As suggested in official documentation you can try with get-pip.py.
wget https://bootstrap.pypa.io/get-pip.py
python3.8 get-pip.py
This will install pip as pip3.8

Another solution would be to install the pip that is in apt. sudo apt install python3-pip. The version of the pip that it installs is for all versions of Python not only for version 3.6 once installed you just need to update the pip with the command python3.8 -m pip install pip and he will be install the latest version of pip for Python.
I would not advise you to remove Python2 because it is an important module for the system you should just create a permanent "alias" in .bashrc for Python3 I did like this alias python="python3.8.

# install py3.8 and dependencies for the pip3 bootstrap script
add-apt-repository -y ppa:deadsnakes/ppa && \
apt install -y python3.8 python3.8-distutils
# download and run the pip3 bootstrap script
cd /tmp && wget https://bootstrap.pypa.io/get-pip.py && \
python3.8 /tmp/get-pip.py
# use pip py3.8 module to install python packages
python3.8 -m pip install numpy pandas

Install python v3.8 as python
RUN apt update --fix-missing && \
apt install python3.8 -y && \
update-alternatives --install /usr/bin/python python /usr/bin/python3.8 10
Install pip for python 3.8
RUN apt install python3-pip -y && \
python -m pip install --upgrade pip

I did this a couple days ago and I struggled a lot with it but I finally got it working, so I wrote up what I did as a blog post.
In the end I think I may have done mostly the same things as the above answer, but if you got lost following it, maybe my screenshots etc will help.
Here's the tl;dr of the process I did:
Uninstall python3-pip & python-pip using apt
Remove the old pip files from /usr/local/bin
Reinstall python3-pip using apt
Add $HOME/.local/bin to your $PATH (also restart your shell to make sure you did this right)

On ubuntu server
sudo apt install python -y
For more information check this blog here.
https://teckresolve.com/install-python-packages-using-pip/

Installing venv for python3 in WSL (Ubuntu)

I am trying to configure venv on Windows Subsystem for Linux with Ubuntu.
What I have tried:
1) Installing venv through pip (pip3, to be exact)
pip3 install venv
I get the following error
ERROR: Could not find a version that satisfies the requirement venv (from versions: none)
ERROR: No matching distribution found for venv
2) Installing venv through apt and apt-get
sudo apt install python3-venv
In this case the installation seems to complete, but when I try to create a virtual environment with python3 -m venv ./venv, I get an error, telling me to do apt-get install python3-venv (which I just did!)
The virtual environment was not created successfully because ensurepip is not
available. On Debian/Ubuntu systems, you need to install the python3-venv
package using the following command.
apt-get install python3-venv
You may need to use sudo with that command. After installing the python3-venv
package, recreate your virtual environment.
Failing command: ['/mnt/c/Users/Vicubso/.../code/venv/bin/python3', '-Im', 'ensurepip', '--upgrade', '--default-pip']
I have also read the following posts
post 1,
post 2, and several others. None of these seem to solve my problem.
Any help would be much appreciated.

Nothing here worked for me, but this did in WSL2:
sudo apt-get update
sudo apt-get install libpython3-dev
sudo apt-get install python3-venv
python3.8 -m venv whatever
Good luck!

Give this approach a shot:
Install the pip:
sudo apt-get install python-pip
Install the virtual environment:
sudo pip install virtualenv
Store your virtual environments somewhere:
mkdir ~/.storevirtualenvs
Now you should be able to create a new virtualenv
virtualenv -p python3 yourVenv
To activate:
source yourVenv/bin/activate
To exit your new virtualenv, just deactivate

This was more of a headache than it needed to be. It seems that it relates to WSL<->Windows file system mapping issues. This blog post perhaps describes it better, but the net is you need to store additional metadata with files on a particular mount, as described in this MS devblog.
I fixed the issue by running:
sudo umount /mnt/c
sudo mount -t drvfs C: /mnt/c -o metadata
After which I was able to create python venv without needing to sudo.

The error occurs when you're in /mnt/XXX (under Windows part).
Switch to Linux part by cd and run python3 -m venv ./venv again and that should be fine

I was getting the same error message, I have WSL(Ubuntu) installed on my computer, finally I found this doc:
https://learn.microsoft.com/en-us/windows/python/web-frameworks#open-a-wsl---remote-window
Ironically the only difference from what I was using as command was the name, I was using venv, then I run the command again using .venv so that the files become hidden files instead, and it worked. Hopefully it'll help someone else :)

You need to install also python3.8-venv via
sudo apt install python3.8-venv
this fixed the problem for me.

How do I install pip3 for Python3 without root privileges on CentOS 7.6? [duplicate]

I want to install pip. It should support Python 3, but it requires setuptools, which is available only for Python 2.
How can I install pip with Python 3?

edit: Manual installation and use of setuptools is not the standard process anymore.
If you're running Python 2.7.9+ or Python 3.4+
Congrats, you should already have pip installed. If you do not, read onward.
If you're running a Unix-like System
You can usually install the package for pip through your package manager if your version of Python is older than 2.7.9 or 3.4, or if your system did not include it for whatever reason.
Instructions for some of the more common distros follow.
Installing on Debian (Wheezy and newer) and Ubuntu (Trusty Tahr and newer) for Python 2.x
Run the following command from a terminal:
sudo apt-get install python-pip
Installing on Debian (Wheezy and newer) and Ubuntu (Trusty Tahr and newer) for Python 3.x
Run the following command from a terminal:
sudo apt-get install python3-pip
Note:
On a fresh Debian/Ubuntu install, the package may not be found until you do:
sudo apt-get update
Installing pip on CentOS 7 for Python 2.x
On CentOS 7, you have to install setup tools first, and then use that to install pip, as there is no direct package for it.
sudo yum install python-setuptools
sudo easy_install pip
Installing pip on CentOS 7 for Python 3.x
Assuming you installed Python 3.4 from EPEL, you can install Python 3's setup tools and use it to install pip.
# First command requires you to have enabled EPEL for CentOS7
sudo yum install python34-setuptools
sudo easy_install pip
If your Unix/Linux distro doesn't have it in package repos
Install using the manual way detailed below.
The manual way
If you want to do it the manual way, the now-recommended method is to install using the get-pip.py script from pip's installation instructions.
Install pip
To install pip, securely download get-pip.py
Then run the following (which may require administrator access):
python get-pip.py
If setuptools is not already installed, get-pip.py will install setuptools for you.

I was able to install pip for python 3 on Ubuntu just by running sudo apt-get install python3-pip.

Python 3.4+ and Python 2.7.9+
Good news! Python 3.4 (released March 2014) ships with Pip. This is the best feature of any Python release. It makes the community's wealth of libraries accessible to everyone. Newbies are no longer excluded by the prohibitive difficulty of setup. In shipping with a package manager, Python joins Ruby, Nodejs, Haskell, Perl, Go--almost every other contemporary language with a majority open-source community. Thank you Python.
Of course, that doesn't mean Python packaging is problem solved. The experience remains frustrating. I discuss this at Does Python have a package/module management system?
Alas for everyone using an earlier Python. Manual instructions follow.
Python ≤ 2.7.8 and Python ≤ 3.3
Follow my detailed instructions at https://stackoverflow.com/a/12476379/284795 . Essentially
Official instructions
Per https://pip.pypa.io/en/stable/installing.html
Download get-pip.py, being careful to save it as a .py file rather than .txt. Then, run it from the command prompt.
python get-pip.py
You possibly need an administrator command prompt to do this. Follow http://technet.microsoft.com/en-us/library/cc947813(v=ws.10).aspx
For me, this installed Pip at C:\Python27\Scripts\pip.exe. Find pip.exe on your computer, then add its folder (eg. C:\Python27\Scripts) to your path (Start / Edit environment variables). Now you should be able to run pip from the command line. Try installing a package:
pip install httpie
There you go (hopefully)!

if you're using python 3.4+
just type:
python3 -m pip

For Ubuntu 12.04 or older,
sudo apt-get install python3-pip
won't work. Instead, use:
sudo apt-get install python3-setuptools ca-certificates
sudo easy_install3 pip

Update 2015-01-20:
As per https://pip.pypa.io/en/latest/installing.html the current way is:
wget https://bootstrap.pypa.io/get-pip.py
python get-pip.py
I think that should work for any version
Original Answer:
wget http://python-distribute.org/distribute_setup.py
python distribute_setup.py
easy_install pip

Single Python in system
To install packages in Python always follow these steps:
If the package is for python 2.x: sudo python -m pip install [package]
If the package is for python 3.x: sudo python3 -m pip install [package]
Note: This is assuming no alias is set for python
Through this method, there will be no confusion regarding which python version is receiving the package.
Multiple Pythons/Virtual Envs
Say you have python3 ↔ python3.6 and python3.7 ↔ python3.7
To install for python3.6: sudo python3 -m pip install [package]
To instal for python3.7: sudo python3.7 -m pip install [package]
This is essentially the same method as shown previously.
Note 1
How to find which python? Do one of the following:
~ » python3 -c "import sys; print(sys.version)"
3.9.5 (default, Nov 18 2021, 16:00:48)
your python3 command spawns:
~ » python3
Python 3.9.5 (default, Nov 18 2021, 16:00:48)
[GCC 10.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>
Notice python 3.9.5 in the second line.
or say you are using virtual env and see where your python points to:
» which python
/home/ganesh/os/np-test/bin/python
Note 2
Change what python3 or python points to: https://askubuntu.com/questions/320996/how-to-make-python-program-command-execute-python-3

python3 -m ensurepip
I'm not sure when exactly this was introduced, but it's installed pip3 for me when it didn't already exist.

Older version of Homebrew
If you are on macOS, use homebrew.
brew install python3 # this installs python only
brew postinstall python3 # this command installs pip
Also note that you should check the console if the install finished successfully. Sometimes it doesn't (e.g. an error due to ownership), but people simply overlook the log.
UPDATED - Homebrew version after 1.5
According to the official Homebrew page:
On 1st March 2018 the python formula will be upgraded to Python 3.x and a python#2 formula will be added for installing Python 2.7 (although this will be keg-only so neither python nor python2 will be added to the PATH by default without a manual brew link --force). We will maintain python2, python3 and python#3 aliases.
So to install Python 3, run the following command:
brew install python3
Then, the pip is installed automatically, and you can install any package by pip install <package>.

If your Linux distro came with Python already installed, you should be able to install PIP using your system’s package manager. This is preferable since system-installed versions of Python do not play nicely with the get-pip.py script used on Windows and Mac.
Advanced Package Tool (Python 2.x)
sudo apt-get install python-pip
Advanced Package Tool (Python 3.x)
sudo apt-get install python3-pip
pacman Package Manager (Python 2.x)
sudo pacman -S python2-pip
pacman Package Manager (Python 3.x)
sudo pacman -S python-pip
Yum Package Manager (Python 2.x)
sudo yum upgrade python-setuptools
sudo yum install python-pip python-wheel
Yum Package Manager (Python 3.x)
sudo yum install python3 python3-wheel
Dandified Yum (Python 2.x)
sudo dnf upgrade python-setuptools
sudo dnf install python-pip python-wheel
Dandified Yum (Python 3.x)
sudo dnf install python3 python3-wheel
Zypper Package Manager (Python 2.x)
sudo zypper install python-pip python-setuptools python-wheel
Zypper Package Manager (Python 3.x)
sudo zypper install python3-pip python3-setuptools python3-wheel

This is the one-liner I copy-and-paste:
curl https://bootstrap.pypa.io/get-pip.py | python3
Alternate:
curl -L get-pip.io | python3
From Installing with get-pip.py:
To install pip, securely download get-pip.py by following this link:
get-pip.py. Alternatively, use
curl:
curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
Then run the following command in the folder where you have downloaded
get-pip.py:
python get-pip.py
Warning: Be cautious if you are using a Python install that is managed
by your operating system or another package manager. get-pip.py does
not coordinate with those tools, and may leave your system in an
inconsistent state.

If you use several different versions of python try using virtualenv http://www.virtualenv.org/en/latest/virtualenv.html#installation
With the advantage of pip for each local environment.
Then install a local environment in the current directory by:
virtualenv -p /usr/local/bin/python3.3 ENV --verbose
Note that you specify the path to a python binary you have installed on your system.
Then there are now an local pythonenvironment in that folder. ./ENV
Now there should be ./ENV/pip-3.3
use
./ENV/pip-3.3 freeze to list the local installed libraries.
use ./ENV/pip-3.3 install packagename to install at the local environment.
use ./ENV/python3.3 pythonfile.py to run your python script.

Here is my way to solve this problem at ubuntu 12.04:
sudo apt-get install build-essential libncursesw5-dev libssl-dev libgdbm-dev libc6-dev libsqlite3-dev tk-dev
Then install the python3 from source code:
wget https://www.python.org/ftp/python/3.4.0/Python-3.4.0.tar.xz
tar xvf Python-3.4.0.tar.xz
cd Python-3.4.0
./configure
make
make test
sudo make install
When you finished installing all of them, pip3 will get installed automatically.

This is what I did on OS X Mavericks to get this to work.
Firstly, have brew installed
Install python 3.4
brew install python3
Then I get the latest version of distribute:
wget https://pypi.python.org/packages/source/d/distribute/distribute-0.7.3.zip#md5=c6c59594a7b180af57af8a0cc0cf5b4a
unzip distribute-0.7.3.zip
cd distribute-0.7.3
sudo setup.py install
sudo easy_install-3.4 pip
sudo pip3.4 install virtualenv
sudo pip3.4 install virtualenvwrapper
mkvirtualenv py3
python --version
Python 3.4.1
I hope this helps.

pip is installed together when you install Python. You can use
sudo pip install (module)
or
python3 -m pip install (module).

Please follow below steps to install python 3 with pip:
Step 1 : Install Python from download here
Step 2 : you’ll need to download get-pip.py
Step 3 : After download get-pip.py , open your commant prompt and go to directory where your get-pip.py file saved .
Step 4 : Enter command python get-pip.py in cmd.
Step 5 : Pip installed successfully , Verify pip installation by type command in cmd pip --version

What’s New In Python 3.4
...
pip should always be available
...
By default, the commands pipX and pipX.Y will be installed on all platforms (where X.Y stands for the version of the Python installation), along with the pip Python package and its dependencies.
https://docs.python.org/3/whatsnew/3.4.html#whatsnew-pep-453
so if you have python 3.4 installed, you can just: sudo pip3 install xxx

For python3 try this:
wget https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py -O - | python
The good thing is that It will also detect what version of python you have (even if it's an environment of python in your custom location).
After this you can proceed normally with (for example)
pip install numpy
source:
https://pypi.python.org/pypi/setuptools/1.1.6#upgrading-from-setuptools-0-6

Assuming you are in a highly restricted computer env (such as myself) without root access or ability to install packages...
I had never setup a fresh/standalone/raw/non-root instance of Python+virtualenv before this post. I had do quite a bit of Googling to make this work.
Decide if you are using python (python2) or python3 and set your PATH correctly. (I am strictly a python3 user.) All commands below can substitute python3 for python if you are python2 user.
wget https://pypi.python.org/packages/source/v/virtualenv/virtualenv-x.y.z.tar.gz
tar -xzvf virtualenv-x.y.z.tar.gz
python3 virtualenv-x.y.z/virtualenv.py --python $(which python3) /path/to/new/virtualenv
source /path/to/new/virtualenv/bin/activate
Assumes you are using a Bourne-compatible shell, e.g., bash
Brilliantly, this virtualenv package includes a standalone version of pip and setuptools that are auto-magically installed into each new virtualenv. This solves the chicken and egg problem.
You may want to create an alias (or update your ~/.bashrc, etc.) for this final command to activate the python virtualenv during each login. It can be a pain to remember all these paths and commands.
Check your version of python now: which python3 should give: /path/to/new/virtualenv/bin/python3
Check pip is also available in the virtualenv via which pip... should give: /path/to/new/virtualenv/bin/pip
Then... pip, pip, pip!
Final tip to newbie Pythoneers: You don't think you need virtualenv when you start, but you will be happy to have it later. Helps with "what if" installation / upgrade scenarios for open source / shared packages.
Ref: https://virtualenv.pypa.io/en/latest/installation.html

To install pip, securely download get-pip.py.
Then run the following:
python get-pip.py
Be cautious if you're using a Python install that's managed by your
operating system or another package manager. get-pip.py does not
coordinate with those tools, and may leave your system in an
inconsistent state.
Refer: PIP Installation

And for Windows 8.1/10 OS Users just open cmd (command prompt)
write this : C:\Users\%USERNAME%\AppData\Local\Programs\Python\Python36-32\Scripts
then
just write this : pip3 install {name of package}
Hint: the location of folder Python36-32 may get different for new python 3.x versions

If you used the command "python get-pip.py", you should have the 'pip' function for Python3. However, 'pip' for Python2 might still be present. In my case I uninstalled 'pip', which removed it from Python2.
After that I ran "python get-pip.py" again. (Make sure that 'get-pip.py' is saved in the same folder as Python3.) The final step was to add the directory with 'pip' command to $PATH. That solved it for me.

=>Easy way to install Python any version on Ubuntu 18.04 or Ubuntu 20.04 follow these steps:-
Step 1: Update Local Repositories:-
sudo apt update
Step 2: Install Supporting Software:-
sudo apt install build-essential zlib1g-dev libncurses5-dev libgdbm-dev libnss3-dev libssl-dev libreadline-dev libffi-dev wget
Step3: Create directory on your home directory To download the newest release of Python Source Code, navigate to the /python-source-files directory and use the wget command:-
mkdir python-source-files
Step 4: Download the Latest Version of Python Source Code:-
wget https://www.python.org/ftp/python/3.7.5/Python-3.7.5.tgz
"you can change python version by just modifies this:-"3.7.5" with the version you want example:-"3.5.2"
Step 5: Extract Compressed Files:-
tar –xf Python-3.7.5.tgz
or
tar xvzf Python-3.7.5.tgz
Step 6: Test System and Optimize Python:-
cd python-3.7.5 or your version of python.
Step 7: Now configure(Using the ––optimization option speeds code execution by 10-20%.):-
./configure ––enable–optimizations
OR you can also do this also if you facing ssl error:-
./configure --with-openssl
Step 8: Install a Second Instance of Python:-
sudo make altinstall
"It is recommended that you use the altinstall method. Your Ubuntu system may have software packages dependent on Python 2.x.
OR
If you want to Overwrite Default Python Installation/version:-
sudo make install"
Step 9:Now check Python Version:-
python3 ––version
Step 10: To install pip for python3 just go with this command:-
sudo apt-get install python3-pip

How to Install pip for python 3.7 on Ubuntu 18?

I've installed Python 3.7 on my Ubuntu 18.04 machine. Following this instructions in case it's relevant:
Download : Python 3.7 from Python Website [1] ,on Desktop and manually
unzip it, on Desktop Installation : Open Terminal (ctrl +shift+T)
Go to the Extracted folder
$ cd ~/Desktop/Python-3.7.0
$ ./configure
$ make
$ sudo make install
Making Python 3.7 default Python :
$ sudo vim ~/.bashrc
press i
on the last and new line - Type
alias python= python3.7
press Esc
type - to save and exit vim
:wq
now type
$ source ~/.bashrc
From here: https://www.quora.com/How-can-I-upgrade-Python-3-6-to-3-7-in-Ubuntu-18-04
I've downloaded several modules through pip install module but when I try to import them, I get a ModuleNotFoundError: No module names 'xx'
So I did some research and apparently when used pip to install, it installed in the modules in previous version of Python.
Somewhere (probably a question in SO) I found a suggestion to install the module using python3.7 -m pip install module but then I get /usr/local/bin/python3.7: no module named pip.
Now I'm stuck, pip is installed, but apparently not for Python 3.7. I'm assuming that if I can install pip for Python 3.7, I can run the pip install command and get the modules I need.
If that is the case, how can I install pip for python 3.7, since it's already installed?
This is the best I have come up with:
I have installed python 3.7 successfully and I can install modules using pip (or pip3) but those modules are installed in Python 3.6 (Comes with ubuntu). Therefore I can't import those modules in python 3.7 (get a module not found)
Python 3.7 doesn't recognize pip/pip3, so I can't install through pip/pip3
I need python 3.7

In general, don't do this:
pip install package
because, as you have correctly noticed, it's not clear what Python version you're installing package for.
Instead, if you want to install package for Python 3.7, do this:
python3.7 -m pip install package
Replace package with the name of whatever you're trying to install.
Took me a surprisingly long time to figure it out, too. The docs about it are here.
Your other option is to set up a virtual environment. Once your virtual environment is active, executable names like python and pip will point to the correct ones.

A quick add-on to mpenkov's answer above (didn't want this to get lost in the comments)
For me, I had to install pip for 3.6 first
sudo apt install python3-pip
now you can install python 3.7
sudo apt install python3.7
and then I could install pip for 3.7
python3.7 -m pip install pip
and as a bonus, to install other modules just preface with
python3.7 -m pip install <module>
EDIT 1 (12/2019):
I know this is obvious for most. but if you want python 3.8, just substitute python3.8 in place of python3.7
EDIT 2 (5/2020):
For those that are able to upgrade, Python 3.8 is available out-of-the-box for Ubuntu 20.04 which was released a few weeks ago.

This works for me.
curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
Then this command with sudo:
python3.7 get-pip.py
Based on this instruction.

I used apt-get to install python3.7 in ubuntu18.04. The installations are as follows.
install python3.7
sudo apt-get install python3.7
install pip3. It should be noted that this may install pip3 for python3.6.
sudo apt-get install python3-pip
change the default of python3 for python3.7. This is where the magic is, which will make the pip3 refer to python3.7.
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.7 1
Hope it works for you.

To install all currently supported python versions (python 3.6 is already pre-installed) including pip for Ubuntu 18.04 do the following:
To install python3.5 and python3.7, use the deadsnakes ppa:
sudo add-apt-repository ppa:deadsnakes/ppa
sudo apt-get update
sudo apt-get install python3.5
sudo apt-get install python3.7
Install python2.7 via distribution packages:
sudo apt install python-minimal # on Ubuntu 18.04 python-minimal maps to python2.7
To install pip use:
sudo apt install python-pip # on Ubuntu 18.04 this refers to pip for python2.7
sudo apt install python3-pip # on Ubuntu 18.04 this refers to pip for python3.6
python3.5 -m pip install pip # this will install pip only for the current user
python3.7 -m pip install pip
I used it for setting up a CI-chain for a python project with tox and Jenkins.

Combining the answers from #mpenkon and #dangel, this is what worked for me:
sudo apt install python3-pip
python3.7 -m pip install pip
Step #1 is required (assuming you don't already have pip for python3) for step #2 to work. It uses pip for Python3.6 to install pip for Python 3.7 apparently.

When i use apt install python3-pip, i get a lot of packages need install, but i donot need them. So, i DO like this:
apt update
apt-get install python3-setuptools
curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
python3 get-pip.py
rm -f get-pip.py

The following steps can be used:
sudo apt-get -y update
---------
sudo apt-get install python3.7
--------------
python3.7
-------------
curl -O https://bootstrap.pypa.io/get-pip.py
-----------------
sudo apt install python3-pip
-----------------
sudo apt install python3.7-venv
-----------------
python3.7 -m venv /home/ubuntu/app
-------------
cd app
----------------
source bin/activate

Install python pre-requisites
sudo apt update
sudo apt install build-essential zlib1g-dev libncurses5-dev libgdbm-dev libnss3-dev libssl-dev libreadline-dev libffi-dev wget
Install python 3.7 (from ppa repository)
sudo add-apt-repository ppa:deadsnakes/ppa
sudo apt update
sudo apt install python3.7
Install pip3.7
sudo apt install python3-pip
python3.7 -m pip install pip
Create python and pip alternatives
sudo update-alternatives --install /usr/local/bin/python python /usr/bin/python3.7 10
sudo update-alternatives --install /usr/local/bin/pip pip /home/your_username/.local/bin/pip3.7 10
Make changes
source ~/.bashrc
python --version
pip --version

For those who intend to use venv:
If you don't already have pip for Python 3:
sudo apt install python3-pip
Install venv package:
sudo apt install python3.7-venv
Create virtual environment (which will be bootstrapped with pip by default):
python3.7 -m venv /path/to/new/virtual/environment
To activate the virtual environment, source the appropriate script for the current shell, from the bin directory of the virtual environment. The appropriate scripts for the different shells are:
bash/zsh – activate
fish – activate.fish
csh/tcsh – activate.csh
For example, if using bash:
source /path/to/new/virtual/environment/bin/activate
Optionally, to update pip for the virtual environment (while it is activated):
pip install --upgrade pip
When you want to deactivate the virtual environment:
deactivate

I installed pip3 using
python3.7 -m pip install pip
But upon using pip3 to install other dependencies, it was using python3.6.
You can check the by typing pip3 --version
Hence, I used pip3 like this (stated in one of the above answers):
python3.7 -m pip install <module>
or use it like this:
python3.7 -m pip install -r requirements.txt
I made a bash alias for later use in ~/.bashrc file as alias pip3='python3.7 -m pip'. If you use alias, don't forget to source ~/.bashrc after making the changes and saving it.

How about simply
add-apt-repository ppa:deadsnakes/ppa
apt-get update
apt-get install python3.7-dev
alias pip3.7="python3.7 -m pip"
Now you have the command
pip3.7
separately from pip3.

curl https://bootstrap.pypa.io/get-pip.py | sudo python3.7
if all else fails.

pip3 not pip. You can create an alias like you did with python3 if you like.

How to install python3.7 and create a virtualenv with pip on Ubuntu 18.04?

I'm trying to set up a standard virtual-environment(venv) with python 3.7 on Ubuntu 18.04, with pip (or some way to install packages in the venv). The standard way to install python3.7 seems to be:
% sudo apt install python3.7 python3.7-venv
% python3.7 -m venv py37-venv
but the second command fails, saying:
The virtual environment was not created successfully because ensurepip
is not available. On Debian/Ubuntu systems, you need to install the
python3-venv package using the following command.
apt-get install python3-venv
You may need to use sudo with that command. After installing the
python3-venv package, recreate your virtual environment.
Failing command: ['/py37-venv/bin/python3.7', '-Im', 'ensurepip',
'--upgrade', '--default-pip']
This is true; there is no ensurepip nor pip installed with this python. And I did install python3.7-venv already (python3-venv is for python3.6 on Debian/Ubuntu). I gather there has been some discussion about this in the python community because of multiple python versions and/or requiring root access, and alternate ways to install python modules via apt or similar.
Creating a venv without pip (--without-pip) succeeds, but then there's no way to install packages in the new venv which seems to largely defeat the purpose.
So what's the accepted "best practice" way to install and use python3.7 on 18.04 with a venv?

I don't know if it's best practices or not, but if I also install python3-venv and python3.7-venv then everything works (this is tested on a fresh stock Debian buster docker image):
% sudo apt install python3.7 python3-venv python3.7-venv
% python3.7 -m venv py37-venv
% . py37-venv/bin/activate
(py37-venv) %
Note that it also installs all of python3.6 needlessly, so I can't exactly say I like it, but at least it does work and doesn't require running an unsigned script the way get-pip.py does.

sudo apt install python3-venv
python3 -m venv env