regex - What exactly do the flags do in the re library for python 3? -


i unable find explanations flags due operations within re library.

https://docs.python.org/3.6/library/re.html

for example, have following bit of python code:

nestedpar = re.findall(r"\([^\(\)]*\)", s, 0)

but unsure happening when change 0 1, since results in crash.

can explain flag means exactly?

the third argument options bit mask, , bit masks defined (this, technically, may vary version version):

sre_flag_template = 1 # template mode (disable backtracking) sre_flag_ignorecase = 2 # case insensitive sre_flag_locale = 4 # honour system locale sre_flag_multiline = 8 # treat target multiline string sre_flag_dotall = 16 # treat target single string sre_flag_unicode = 32 # use unicode locale sre_flag_verbose = 64 # ignore whitespace , comments sre_flag_debug = 128 # debugging

using simple bitwise or (or regular +) can combine multiple flags (e.g. re.multiline | re.dotall). shouldn't fail on 1 please don't use numbers directly, assigned meaningful constants reason.

edit - template mode (re.t or re.template), flag 1 shown above, experimental , lot of things can go wrong it, directly source:

# sre extensions (experimental, don't rely on these) t = template = sre_compile.sre_flag_template # disable backtracking

so you've encountered problem templating mode. either way happy life, not set flags :)


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