Sometimes, we need to generate filenames with current date in their file names. Windows command prompt supports variable substrings. For example, my command prompt prints 2021_25_02.txt for command echo %DATE:~10,4%_%DATE:~7,2%_%DATE:~4,2%.txt. The output is based on my Regional settings.
I thought this is natively supported by Windows, but it turned out it is not. I assumed the following code will natively work in python, but it raises exception:
>>> fh = open(r'j:\%DATE:~10,4%_%DATE:~7,2%_%DATE:~4,2%.txt', 'w')
IOError: [Errno 22] invalid mode ('w') or filename: 'j:\\%DATE:~10,4%_%DATE:~7,2%_%DATE:~4,2%.txt'
I am able to do workaround with subprocess module as follows:
>>> import subprocess
>>> name = r'j:\%DATE:~10,4%_%DATE:~7,2%_%DATE:~4,2%.txt'
>>> final_name = subprocess.Popen(['echo', name], stdout=subprocess.PIPE, shell=True).communicate()[0].strip()
>>> print(final_name)
j:\2021_25_02.txt
Is there more simple or pythonic way to make command prompt variable substrings work?