I am using requirement.txt to specify the package dependencies that are used in my python application. And everything seems to work fine for packages of which either there are no internal dependencies or for the one using the package dependencies which are not already installed.
The issue occurs when i try to install a package which has a nested dependency on some other package and an older version of this package is already installed.
I know i can avoid this while installing a package manually bu using pip install -U --no-deps <package_name>. I want to understand how to do this using the requirement.txt as the deployment and requirement installation is an automated process.
Note:
The already installed package is not something i am directly using in my project but is part of a different project on the same server.
Thanks in advance.
Dependency resolution is a fairly complicated problem. A requirements.txt just specifies your dependencies with optional version ranges. If you want to "lock" your transitive dependencies (dependencies of dependencies) in place you would have to produce a requirements.txt that contains exact versions of every package you install with something like pip freeze. This doesn't solve the problem but it would at least point out to you on an install which dependencies conflict so that you can manually pick the right versions.
That being said the new (as of writing) officially supported tool for managing application dependencies is Pipenv. This tool will both manage the exact versions of transitive dependencies for you (so you won't have to maintain a "requirements.txt" manually) and it will isolate the packages that your code requires from the rest of the system. (It does this using the virtualenv tool under the hood). This isolation should fix your problems with breaking a colocated project since your project can have different versions of libraries than the rest of the system.
(TL;DR Try using Pipenv and see if your problem just disappears)
I'm having a hard time setting up python packages. EasyInstall from SetupTools is supposed to help that, but they don't have an executable for Python 2.6.
For instance to install Mechanize, I'm just supposed to put the Mechanize folder in C:\Python24\Lib\site-packages according to INSTALL.txt, but runnning the tests does not work. Can someone help shed some light on this? Thanks!
The accepted answer is outdated. So first, pip is preferred over easy_install, (Why use pip over easy_install?). Then follow these steps to install pip on Windows, it's quite easy.
Install setuptools:
curl https://bootstrap.pypa.io/ez_setup.py | python
Install pip:
curl https://bootstrap.pypa.io/get-pip.py | python
Optionally, you can add the path to your environment so that you can use pip anywhere. It's somewhere like C:\Python33\Scripts.
Newer versions of Python for Windows come with the pip package manager. (source)
pip is already installed if you're using Python 2 >=2.7.9 or Python 3 >=3.4
Use that to install packages:
cd C:\Python\Scripts\
pip.exe install <package-name>
So in your case it'd be:
pip.exe install mechanize
This is a good tutorial on how to get easy_install on windows. The short answer: add C:\Python26\Scripts (or whatever python you have installed) to your PATH.
You don't need the executable for setuptools.
You can download the source code, unpack it, traverse to the downloaded directory and run python setup.py install in the command prompt
Starting with Python 2.7, pip is included by default. Simply download your desired package via
python -m pip install [package-name]
As I wrote elsewhere
Packaging in Python is dire. The root cause is that the language ships without a package manager.
Fortunately, there is one package manager for Python, called Pip. Pip is inspired by Ruby's Gem, but lacks some features. Ironically, Pip itself is complicated to install. Installation on the popular 64-bit Windows demands building and installing two packages from source. This is a big ask for anyone new to programming.
So the right thing to do is to install pip. However if you can't be bothered, Christoph Gohlke provides binaries for popular Python packages for all Windows platforms http://www.lfd.uci.edu/~gohlke/pythonlibs/
In fact, building some Python packages requires a C compiler (eg. mingw32) and library headers for the dependencies. This can be a nightmare on Windows, so remember the name Christoph Gohlke.
I had problems in installing packages on Windows. Found the solution. It works in Windows7+. Mainly anything with Windows Powershell should be able to make it work. This can help you get started with it.
Firstly, you'll need to add python installation to your PATH variable. This should help.
You need to download the package in zip format that you are trying to install and unzip it. If it is some odd zip format use 7Zip and it should be extracted.
Navigate to the directory extracted with setup.py using Windows Powershell (Use link for it if you have problems)
Run the command python setup.py install
That worked for me when nothing else was making any sense. I use Python 2.7 but the documentation suggests that same would work for Python 3.x also.
Upgrade the pip via command prompt ( Python Directory )
D:\Python 3.7.2>python -m pip install --upgrade pip
Now you can install the required Module
D:\Python 3.7.2>python -m pip install <<yourModuleName>>
pip is the package installer for python, update it first, then download what you need
python -m pip install --upgrade pip
Then:
python -m pip install <package_name>
You can also just download and run ez_setup.py, though the SetupTools documentation no longer suggests this. Worked fine for me as recently as 2 weeks ago.
PS D:\simcut> C:\Python27\Scripts\pip.exe install networkx
Collecting networkx
c:\python27\lib\site-packages\pip\_vendor\requests\packages\urllib3\util\ssl_.py:318: SNIMissingWarning: An HTTPS reques
t has been made, but the SNI (Subject Name Indication) extension to TLS is not available on this platform. This may caus
e the server to present an incorrect TLS certificate, which can cause validation failures. You can upgrade to a newer ve
rsion of Python to solve this. For more information, see https://urllib3.readthedocs.io/en/latest/security.html#snimissi
ngwarning.
SNIMissingWarning
c:\python27\lib\site-packages\pip\_vendor\requests\packages\urllib3\util\ssl_.py:122: InsecurePlatformWarning: A true SS
LContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL con
nections to fail. You can upgrade to a newer version of Python to solve this. For more information, see https://urllib3.
readthedocs.io/en/latest/security.html#insecureplatformwarning.
InsecurePlatformWarning
Downloading networkx-1.11-py2.py3-none-any.whl (1.3MB)
100% |################################| 1.3MB 664kB/s
Collecting decorator>=3.4.0 (from networkx)
Downloading decorator-4.0.11-py2.py3-none-any.whl
Installing collected packages: decorator, networkx
Successfully installed decorator-4.0.11 networkx-1.11
c:\python27\lib\site-packages\pip\_vendor\requests\packages\urllib3\util\ssl_.py:122: InsecurePlatformWarning: A true SSLContext object i
s not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. You can upgrade
to a newer version of Python to solve this. For more information, see https://urllib3.readthedocs.io/en/latest/security.html#insecureplat
formwarning.
InsecurePlatformWarning
Or just put the directory to your pip executable in your system path.
As mentioned by Blauhirn after 2.7 pip is preinstalled. If it is not working for you it might need to be added to path.
However if you run Windows 10 you no longer have to open a terminal to install a module. The same goes for opening Python as well.
You can type directly into the search menu pip install mechanize, select command and it will install:
If anything goes wrong however it may close before you can read the error but still it's a useful shortcut.
I am pretty new to python, my background is with VB visual studios, I am trying to develop a app in which I want to consume WCF service. Found Suds is the required python module.
I am using Kivy 1.8.0 and Eclipse with pydev on Windows 7 64bit. Could you please point me in correct direction on how to instal the package, found no exe, I have run the setup.py from suds but did not work.
Any advice/direction towards tutorial is of great help.
Are you by any chance running the Python 3 version of Kivy? Suds looks like it is abandondonware (last release in 2010) and likely does not have a Python3 port. You may have luck with the Python2.7 version of Kivy and pip installing suds, but keep in mind you will be relying on an apparently unsupported module (suds) for your project.
The best tool to install Python modules is pip.
With pip you don't even need to download installed module because it get it from remote repository.
pip search suds
pip install suds
Maybe you have pip installed with Python.
Otherwise see page https://pypi.python.org/pypi/pip
BTW: Of couser not all modules are available by pip but this way you can get most modules.
EDIT:
Installion suds with pip looks (on Linux) like this:
$ pip install suds
Downloading/unpacking suds
Downloading suds-0.4.tar.gz (104kB): 104kB downloaded
Running setup.py egg_info for package suds
Installing collected packages: suds
Running setup.py install for suds
/usr/bin/python -O /tmp/tmp5qxEid.py
removing /tmp/tmp5qxEid.py
Successfully installed suds
Cleaning up...
Until today, I have been using the macports version of python27 and installing python packages through macports. Today, I needed some packages which were not available through macports; I learned about pip and found them there. After installing these packages through pip, however, I realized that neither pip nor macports could see what had been installed by the other. So, for consistency, I decided to uninstall all macports packages, install python27 and py27-pip through macports and then proceed to install all of my python packages through pip.
This worked fine, but since macports does not know about my pip-installed python packages, I ran into trouble when installing something else which depends on python (e.g., inkscape): macports tried to install its own version of, e.g. py27-numpy (already installed by pip) and then failed installation because it "already exists and does not belong to a registered port."
Is there a consistent way to use pip and to get macports to recognize that the python packages it might need for something else are already installed?
The solution is: dont use Macports for installing Python's packages.
Macports is a general package manager and it registers installed packages in its database.
Pip is a package manager for Python so if you want to install Python package, use appropriate package management tool. Pip doesnt have it's own database to keep evidence about installed stuff - it just checks Python's path to see if the package is there (and that's what you want).
Sooner or later you'll use Virtualenv anyway and you'll need pip to install packages in there too so it's better to use it everywhere.
The output of pip freeze on my machine has included the following odd line:
command-not-found==0.2.44
When trying to install requirements on a different machine, I got the obvious No distributions at all found for command-not-found==0.2.44. Is this a pip bug? Or is there any real python package of that name, one which does not exist in pypi?
Indeed, as mentioned in the follow up comments, Ubuntu has a python package, installed via dpkg/apt that is called "python-commandnotfound"
$apt-cache search command-not-found
command-not-found - Suggest installation of packages in interactive bash sessions
command-not-found-data - Set of data files for command-not-found.
python-commandnotfound - Python 2 bindings for command-not-found.
python3-commandnotfound - Python 3 bindings for command-not-found.
As this is provided via apt, and not available in the pypi repo, you won't be able to install it via pip, but pip will see that it is installed. For the purposes of showing installed packages, pip doesn't care if a package is installed via apt, easy_install, pip, manually, etc.
In short, if you actually need it on another host (which I assume you don't) you'll need to apt-get install python-commandnotfound.