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How to escape single quotes within single quoted strings
(25 answers)
When to wrap quotes around a shell variable?
(5 answers)
Closed last year.
I'm trying to process an input string in a Python script which is taken as a command line argument. This input might contain quotes as well (both single and double is possible) and I'm not able to provide it as input. I tried escaping it (with \), does not work.
Here are the details:
python3 code.py --foo="foo" //works
python3 code.py --foo='foo' //works
python3 code.py --foo='f"o"o' //works
python3 code.py --foo="fo'o'" //works
python3 code.py --foo="fo\"o" //does not work
python3 code.py --foo='fo\'o' //does not work
For my use case, there could also be a mixture of single or double quotes as well. Is there a workaround?
If it matters, here is the relevant code:
import argparse
parser = argparse.ArgumentParser(description="Demo")
parser.add_argument("--foo", required=True)
args = parser.parse_args()
print(args.foo)
Here is what happens when I try and run using input that "does not work":
$ python3 code.py --foo='v\'1'
> ^C
I get a "prompt", which I then exit by ctrl-C. Basically, \ does not escape the (middle) quote, and bash identifies my command as incomplete.
In a unix shell, to easily figure out the exact string you need to send to any commandline argument, you can use Python's shlex.quote():
>>> import shlex
>>> arg = r'''"fo\"o"'''
>>> print(shlex.quote(arg))
'"fo\"o"'
Make sure you wrap the argument with r and triple quotes.
If you happen to have triple quotes in your string, you'll have to manually escape everything without using r.
Related
This question already has answers here:
How to fix "<string> DeprecationWarning: invalid escape sequence" in Python?
(2 answers)
Closed 1 year ago.
So, as SO keeps suggesting me, I do not want to replace double backslashes, I want python to understand them.
I need to copy files from a windows distant directory to my local machine.
For example, a "equivalent" (even if not) in shell (with windows paths):
cp \\directory\subdirectory\file ./mylocalfile
But python does not even understand double backslashes in strings:
source = "\\dir\subdir\file"
print(source)
$ python __main__.py
__main__.py:1: DeprecationWarning: invalid escape sequence \s
source = "\\dir\subdir\file"
\dir\subdir
ile
Is Python able to understand windows paths (with double backslashes) in order to perform file copies ?
You can try this also:
source = r"\dir\subdir\file"
print(source)
# \dir\subdir\file
You can solve this issue by using this raw string also.
What we are doing here is making "\dir\subdir\file" to raw string by using r at first.
You can visit here for some other information.
raw strings are raw string literals that treat backslash (\ ) as a literal character. For example, if we try to print a string with a “\n” inside, it will add one line break. But if we mark it as a raw string, it will simply print out the “\n” as a normal character.
I have to run a python script within bash, passing it a string which is stored in a variable... so inside bash I have:
python my_script.py $myvariable
myvariable is a string that can contain single/double quotes which I would preserve (since I make some splits in python script using that quotes). How could I preserve that quotes? Can I escape them somehow before passing to python? I know that I could surround myvariable too with single/double quotes, but I don't know the content of the string, so it would be faulty.
I have this input:
python script.py --key '("music","aaa")' --date '("01/01/1990",0,0)'
And I do:
constrain = literal_eval(sys.argv[2])
print(type(constrain))
print(type(sys.argv[4]))
And all outputs are str while they should be tuples. The input cannot be changed!
You're command line should work perfectly from MSYS or Linux, but here you're running it from windows shell.
Windows shell doesn't treat simple quotes as syntatcic. They're passed literally to your python code. To top it all, the double quotes are removed which makes your second arg '(music,aaa)' when passed to python: no way you can literal_eval that. So your input string has to be changed (or your operating system :))
Do this to call your code:
python script.py --key "(""music"",""aaa"")" --date "(""01/01/1990"",0,0)"
You have to quote the arguments and double the quotes in the arguments. And use double quotes exclusively.
EDIT: or even better (would work on both Linux and Windows): use simple quotes inside your arguments, double quotes outside (literal_eval is not json: it understands both simple & double quotes!):
python script.py --key "('music','aaa')" --date "('01/01/1990',0,0)"
now I'm getting:
<type 'tuple'>
<type 'str'>
(you get str because the 4th argument is always a string, you probably forgot to literal_eval it)
and print(constrain) yields:
('music', 'aaa')
(so it's not a python issue, rather a CMD issue)
I'm trying to read command line arguments in python in the form:
python myprogram.py string string string
I have tried using sys.argv[1-3] to get each string, but when I have a string such as $unny-Day, it does not process the entire string. How can I process strings like these entirely?
Are you using a shell? $ is a special character in the shell that is interpreted as a shell variable. Since the variable does not exist, it is textually substituted with an empty string.
Try using single quotes around your parameter, like > python myapp.py '$unny-Day'.
I have a quick question. I got the following bash script from my friend, but I don't know what /inline/b64/ is, and how the following code segment works.
I have some experience with bash, and Python, but I cannot understand the following code fragment at all. Could anyone please give me some enlightenment?
More specifically,
1) What does /inline/b64 mean? I did some search on the web, but I couldn't find any clues.
2) What does the following command mean?
ENCODED_COMMAND=$(python <<EOF
3) What's the purpose of these kinds of encoding?
#!/bin/bash
COMMAND="FILTER file utterance_id /tmp/my_utt_list"
ENCODED_COMMAND=$(python <<EOF
import base64
print base64.urlsafe_b64encode('$COMMAND')
EOF
)
$BIN --edit_commands="/inline/b64/$ENCODED_COMMAND"
This depends on what the value of $BIN is. Presumably this is some other script which supports an --edit_commands flag. You would need to what that other script is expecting for this value to be able to interpret it.
This is combining a couple of bits of bash syntax. First, $(...) means "execute the enclosed command and capture its output as a string". Second, the <<EOF means that the following lines until the second EOF should be passed to the standard input of the command. So taken together, this is executing the Python script between the two EOFs, capturing its output, and assigning it to the ENCODED_COMMAND variable.
The script is taking some string, $COMMAND, and using the Python base64.urlsafe_b64encode function to encode it with Base64. The encoded string is then being passed to some unknown command, $BIN, which will presumably do something with it — perhaps decode and execute it in some way.