[Python] Regex: validating repeated cmd-line options

I am using Python re to validate a command line options.

This is the portion that is giving me hard times: a repeated, or non-mandatory, -c snake_case=1-like option.

I tried to fake the regex engine by adding a hard-coded extra option, at the cost of an further post-processing cleaning operation, with no success.

Then I also tried to truncate the length of each option, keeping the regex invariant, and it works... but, of course, I cannot use it in my project.

How should I build a reliable regex to handle the problem?

import re


# regex
r = r'(?:-c\s[a-z_]+=1\s?)*'

# real case: failure
cmd = '-c tessedit_write_images=1 -c wordrec_display_segmentations=1'
print(re.search(r, cmd))
#<re.Match object; span=(0, 27), match='-c tessedit_write_images=1 '>


# fake case: truncated length of options: correct result
cmd = '-c dit_write_images=1 -c wrec_display_segm=1'
print(re.search(r, cmd))
#<re.Match object; span=(0, 44), match='-c dit_write_images=1 -c wrec_display_segm=1'>

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