I'm working on Windows. I've a Python file to create a new CSV file and I view that using Notepad (even through Microsoft Excel).
import csv
data = [['fruit','quantity'], ['apple',5], ['banana',7],['mango',8]]
with open('d:\lineter.csv', 'w') as l:
w = csv.writer(l,delimiter='|', lineterminator='\r')
w.writerows(data)
The resulting file in Notepad:
fruit|quantityapple|5banana|7mango|8
Does the carriage return \r work or not? It works like lineterminator='' in Notepad. But in Excel, it works like '\n'.
The output doesn't seem to implement carriage return. When I use lineterminator as:
w = csv.writer(l, delimiter='|', lineterminator='*\r*\n')
The output in Notepad is:
fruit|quantity**
apple|5**
banana|7**
mango|8**
This is evident here too.
How does '\r' work in lineterminator in writer()?
Or is there another thing happening there?
The shorter answer:
When to use carriage return (CR, \r) vs. line feed (LF, \n) vs. both (CRLF, \r\n) to make a new line appear in a text editor on Windows, Mac, and Linux:
How does '\r' work in lineterminator in writer()??
It works fine in csv.writer(). This really isn't a Python, CSV, or writer problem. This is an operating system historical difference (actually, it's more accurate to state it is a program-specific difference) going back to the 1960s or so.
Or is there another thing happening there?
Yes, this is the one.
Your version of Notepad doesn't recognize a carriage return (\r) as a character used to display new lines, and hence won't display it as such in Notepad. Other text editors, such as Sublime Text 3, however probably would, even on Windows.
Up until about the year 2018 or so, Windows and Notepad required a carriage return + line feed (\r\n) together to display a new line. Contrast this to Mac and Linux, which require only \n.
The solution is to use \r\n for a new line on Windows, and \n alone for a new line on Mac or Linux. You can also try a different text editor, such as Sublime Text, when viewing or editing text files, or upgrade your version of Windows or Notepad, if possible, as somewhere around the year 2018 Windows Notepad started to accept \r alone as a valid old-Mac-style new line char.
(from the OP's comment under this answer):
Then why to give '\r\n'???
When a programmer writes a program, the programmer can make the program do whatever the programmer wants the program to do. When Windows programmers made Windows and Notepad they decided to make the program do nothing if it got a \r, nothing if it got a \n, and to do a new line if it got a \r\n together. It's that simple. The program is doing exactly what the programmers told it to do, because they decided that's how they wanted the program to work. So, if you want a new line in the older (pre-2018) version of Notepad in Windows, you must do what the programmers require you to do to get it. \r\n is it.
This goes back to the days of teletypewriters (read the "History" and "Representation" sections here), and this page about "teleprinters" / "teletypewriters" / "teletype or TTY machines" too:
A typewriter or electromechanical printer can print characters on paper, and execute operations such as move the carriage back to the left margin of the same line (carriage return), advance to the same column of the next line (line feed), and so on.
(source; emphasis added)
The mechanical carriage return button on a teletypewriter (\r now on a computer) meant: "return the carriage (print head) to the beginning of the line" (meaning: the far left side of the page), and the line feed mechanical mechanism on a teletypewriter (\n now on a computer) meant: "roll the paper up one line so we can now type onto the next line." Without the mechanical line feed (\n) action, the carriage return (\r) alone would move the mechanical print head to the far left of the page and cause you to type right back on top of the words you already typed! And without the carriage return mechanical action (\r on a computer), the line feed mechanical action (\n) alone would cause you to just type in the last column at the far right on each new line on the page, never able to return the print head to the left side of the page again! On an electro-mechanical teletypewriter, they both had to be used: the carriage return would bring the print head back to the left side of the page, and the line feed action would move the print head down to the next line. So, presumably, Windows programmers felt it was logical to keep that tradition alive, and they decided to require both a \r\n together to create a new line on a computer, since that's how it had to be done traditionally on an electro-mechanical teletypewriter.
Read below for details.
Details (the longer answer):
I have some ideas of what's going on, but let's take a look. I believe we have two questions to answer:
Is the \r actually being stored into the file?
Is Notepad actually showing the \r, and if not, why not?
So, for #1. Let's test it on Linux Ubuntu 20.04 (Focal Fossa):
This program:
#!/usr/bin/python3
import csv
data = [['fruit','quantity'], ['apple',5], ['banana',7],['mango',8]]
with open('d:\lineter.csv','w') as l:
w = csv.writer(l, delimiter='|', lineterminator='\r')
w.writerows(data)
produces this file: d:\lineter.csv. If I open it in the Sublime Text 3 text editor I see:
fruit|quantity
apple|5
banana|7
mango|8
So far so good. Let's look at the characters with hexdump at the command line:
hexdump -c shows the \r characters, sure enough!
$ hexdump -c d\:\\lineter.csv
0000000 f r u i t | q u a n t i t y \r a
0000010 p p l e | 5 \r b a n a n a | 7 \r
0000020 m a n g o | 8 \r
0000028
You can also use hexdump -C to show the characters in hexadecimal instead, and again, I see the \r in the file as a hex 0d char, which is correct.
Ok, so I boot up Windows 10 Professional in my VirtualBox virtual machine in Linux, and open the same file in Notepad, and....it works too! See screenshot:
But, notice the part I circled which says "Macintosh (CR)". I'm running the latest version of Windows 10 Professional. I'm betting you're using an old version of Notepad which doesn't have this fix, and yours won't say that here. This is because for 33 years Notepad didn't handle Carriage Return, or \r, as a valid line-ending, so it wouldn't display it as such. See here: Windows Notepad fixed after 33 years: Now it finally handles Unix, Mac OS line endings.
Due to historical differences dating back to teletypewriters and Morse code (read the "History" and "Representation" sections here), different systems decided to make their text editors treat line endings in different ways. From the article just above (emphasis added):
Notepad previously recognized only the Windows End of Line (EOL) characters, specifically Carriage Return (CR, \r, 0x0d) and Line Feed (LF, \n, 0x0a) together.
For old-school Mac OS, the EOL character is just Carriage Return (CR, \r, 0x0d) and for Linux/Unix it's just Line Feed (LF, \n, 0x0a). Modern macOS, since Mac OS X, follows the Unix convention.
So, what we have here is the following displayed as a newline in a text editor:
Old-school Mac: CR (\r) only
Windows Notepad up until ~2018: CR & LF together (\r\n)
Linux: LF (\n) only
Modern Mac: LF (\n) only
Modern Windows Notepad (year ~2018 and later): any of the scenarios above.
So, for Windows, just stick to always using \r\n for a newline, and for Mac or Linux, just stick to always using \n for a newline, unless you're trying to guarantee old-school (i.e., pre-2019 :)) Windows compatibility of your files, in which case you should use \r\n for newlines as well.
Note, for Sublime Text 3, I just searched the preferences in Preferences → Settings and found this setting:
// Determines what character(s) are used to terminate each line in new files.
// Valid values are 'system' (whatever the OS uses), 'windows' (CRLF) and
// 'unix' (LF only).
"default_line_ending": "system",
So, to use the convention for whatever OS you're running Sublime Text on, the default is "system". To force 'windows' (CRLF) line endings when editing and saving files in Sublime Text, however, use this:
"default_line_ending": "windows",
And to force Unix (Mac and Linux) LF-only line ending settings, use this:
"default_line_ending": "unix",
In the Notepad editor, I can find no such settings to configure. It is a simple editor, catering for 33 years to Windows line endings only.
Additional Reading:
https://en.wikipedia.org/wiki/Teleprinter
https://en.wikipedia.org/wiki/Newline#History
Is a new line = \n OR \r\n?
Why does Windows use CR LF?
[I still need to read & study] Unix & Linux: Why does Linux use LF as the newline character?
[I still need to read & study] Retrocomputing: Why is Windows using CR+LF and Unix just LF when Unix is the older system?
In Pycharm I keep running into this error:
TabError: inconsistent use of tabs and spaces in indentation
I know its a problem with tabs/spaces.
I want:
if len(myresults)==0:
print("TEST")
Whenever I type, pressing enter after every line typed I actually type:
if len(myresults)==0:
print("TEST")
Causing this error. How do I fix it? Here are my setting s for pycharm:
Pycharm Settings
I'm probably missing something obvious, but I simply cannot find it.
Try,
In the "Settings | Editor | Code Style" -- try disabling "Detect and use existing file indents for editing" in case if you have it enabled (it is by default). NOTE: re-opening file in editor may be required.
Do you have any .editorconfig files anywhere in the path of that file? Settings from .editorconfig have priority (will overwrite) over your IDE settings.
Go to Settings --> Editor --> Code Style --> Python --> Tabs and Idents.
Here activate (checkbox) Use tab character AND Smart tabs
Thats works for me.
What worked for me:
"Settings | Editor | Code Style" -- disable "Detect and use existing file indents for editing" (as #Nipun Sampath suggestted)
Together with:
"Settings | Editor | Code Style | Python" -- disable "Use tab character"
For reformatting the file: Ctr+Alt+L -> 'Code cleanup' on either selected text or whole file (depending on what is needed)
I'm using Pycharm and Jupyter Notebook and had the same problem with both of them. I could not fix it with "convert Indents", So I uninstalled some of the modules that I was using in my programm and reinstall them and worked for me.
I'm using Pycharm 2019.1. For me, this error constantly appeared always I pressed Enter to write a new line, and I have to manually rewrite every indentation in order to disappear
the red sub-lines that indicate error. I fixed it by analyzing the full code into another text editor (kate editor in my case, but you can use another one). I verified there's some indentations written as [TAB] and the most of them written as four simple spaces. So I replaced all indentations written as [TAB] by indentations written as four spaces (most of the editors replace by using [Ctrl R] shortcut) and... voilà. Everything works fine.
Note: I couldn't do the replace into Pycharm editor itself. Apparently pycharm editor does not differentiate a [Tab] of four spaces when you try replace by [Ctrl R].
Hope it help future users.
I want to introduce a tab character in the new line for creating a new block in vim for python files.
Example
when I write
if(a < 5):
and press Enter, the cursor should come in next line with a tab after if in vertical alignment from the above line. Something like this
if(a < 5):
a = 5
I have configured my .vimrc file like this
set nu
set autoindent
set tabstop=4
syntax enable
set showmatch
colorscheme gruvbox
set bg=dark
"automatically creates a block after :
autocmd FileType python inoremap :<CR> :<CR><Tab>
Note:
1) Last line, I have written for the intended purpose mentioned in my question.
2) autoindent is set.
3) I dont want to use any plugin.
Problem I am facing:
When I press Enter after : , in addition to tab, one extra space is also created which creates wrong indentation.
Thanks in advance for helping
The way you're trying to do this is the hard way. There's a filetype plugin and a Python syntax type and it already knows what to do.
filetype plugin indent on
And don't use set autoindent. It's not very intelligent, it just copies the indent from the previous line. It's the opposite of what you're trying to do.
Files ending in .py should automatically get the right settings. If you need to force the current syntax type in a buffer, you can do that with
:set filetype=python
If you want to use tabs instead of spaces,
" Globally
set noexpandtab
" Python only
autocmd FileType python set noexpandtab
However, I'll note that using tabs in Python is not recommended and goes against published best practices (see PEP 8).
Lastly I'll mention that "plugin" is just a Vim term. All of this ships with Vim by default, this does not create a third-party dependency.
When I create the file test.py (see code below) in an editor on Windows (I tried Netbeans, PyCharm and Notepad++) and upload it to the server (Ubuntu) I receive this error:
End of script output before headers: test.py
But when I create the file directly on the server using vi command line editor the page is displayed without any error. Any idea how to fix this issue ?
Here's the code for test.py
#!/usr/bin/python
# send content type
print("Content-Type: text/html\n\n")
print("Good")
I think that's because of windows carriage return characters.
These are two characters:
\r is carriage return;
\n is line feed.
Two characters combined represent a new line on Windows. Whereas on Linux, \n represents new line.
Notepad++ has an option to specify which format you want to use:
Go to Settings -- > Preferences and the choose linux:
Does anyone know how Python deals with ConfigParser line endings in the different OSes? Because it follows the Windows INI format. But what about Linux?
(As you know, Windows text line endings are typically CRLF, and Unix's are CR.)
I want users of my app to take their config files (.INI files) easily from Windows to Linux and I'd like to know if that's going to be problematic.
If it does use different line endings for Unix and Windows, what do you recommend?
You're fine, ConfigParser will still work.
The reason is that is uses fp.readline, which reads up to and including the next LF (\n). The value is then stripped of whitespace, which removes the CR (\r).
I'd say just use LF (\n) as your line separator - it will work on both systems, but using both won't cause any harm either.
Edit: In fact, if you generate a file using ConfigParser.RawConfigParser it will use \n as the line separator.