Calling batch commands from python-CodePudding

I am using python with some external program API in order to automate some stuff. Have in mind that these "extpro" and "--file" and "--dont-breakaway-from-job" are built in commands that I have to use, my code looks like this:

send = os.system('extpro --file '(os.path.join(base_dir, extpr_path))' --dont-breakaway-from-job')

Error that I am getting is on the --dont-breakaway-from-job, saying Expected ")" pylance.

But when I try this there is no error:

send = os.system('extpro --file "C:/user/program/run.exe" --dont-breakaway-from-job')

Anyone have idea what might be behind this behavior? Is there a way maybe to split whole command into two or three?

Any advice is welcome, thanks!

CodePudding user response：

os.path.join returns str object, thus your

'extpro --file '(os.path.join(base_dir, extpr_path))' --dont-breakaway-from-job'

expands into:

'extpro --file '"<whatever that path is>"' --dont-breakaway-from-job'
               ^

In the position marked with ^ the string ends. And, since os.system expects only one single parameter, pylance (and interpreter too) supposes, that this parameter is already passed and throws an error, that closing bracket is expected.

Interpreter doesn't concatenate os.path.join result with string before it, because it doesn't know, that os.path.join is a string. Function call will become string only in runtime.

However, your second variant contains 'some str "inner str" some more'. Python interpreter sees string, starting with ' (single qotation mark) and looks for a matching pair, that will mean end of the string. All " (double quotation marks) between single ones are considered part of the string.

Solution is simple. You can do any of:

# Concatenating strings with  
send = os.system('extpro --file "'  os.path.join(base_dir, extpr_path)   '" --dont-breakaway-from-job')
# Using format (or f-strings, ifyou're using python 3.6 )
send = os.system('extpro --file "{}" --dont-breakaway-from-job'.format(os.path.join(base_dir, extpr_path)))
# or
send = os.system(f'extpro --file "{os.path.join(base_dir, extpr_path)}" --dont-breakaway-from-job')

In any of 3 variations it's worth wrapping os.path.join results with " (double quotation mark) in case it contains spaces or other undesired symbols, that may e parsed incorrectly

CodePudding user response：

Your line send = os.system('extpro --file '(os.path.join(base_dir, extpr_path))' --dont-breakaway-from-job') doesn't create the string that you expect/need and doesn't concatenate 'extpro --file ' with the filepath (within "!) and the ' --dont-breakaway-from-job').

The easiest solution might be to use a F-string:

send = os.system(f'extpro --file "{os.path.join(base_dir, extpr_path)}" --dont-breakaway-from-job')

Important here is also to add " to the string, since os.path.join(...) doesn't create a string with the ".

CodePudding user response：

If i understood it right, the issue is that you need to concatenate the string with quotation marks? If that is the case, you can use the following

send = os.system("extpro --file \"" os.path.join(base_dir, extpr_path) "\" --dont-breakaway-from-job")

The os.path.join returns a string which needs to be concatenated using . Furthermore, you need to include quotation marks around os.path.join. This can be achieved in many ways, but the one i used in this answer is \".