Converting from a string to boolean in Python?

def str2bool(v):
  return v.lower() in ("yes", "true", "t", "1")

Then call it like so:

>>> str2bool("yes")
True
>>> str2bool("no")
False
>>> str2bool("stuff")
False
>>> str2bool("1")
True
>>> str2bool("0")
False

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Handling true and false explicitly:

You could also make your function explicitly check against a True list of words and a False list of words. Then if it is in neither list, you could throw an exception.

Really, you just compare the string to whatever you expect to accept as representing true, so you can do this:

s == 'True'

Or to checks against a whole bunch of values:

s.lower() in ['true', '1', 't', 'y', 'yes', 'yeah', 'yup', 'certainly', 'uh-huh']

Be cautious when using the following:

>>> bool("foo")
True
>>> bool("")
False

Empty strings evaluate to False, but everything else evaluates to True. So this should not be used for any kind of parsing purposes.

Warning: This answer will no longer work as of Python 3.12 (it's deprecated as of 3.10)

Use:

bool(distutils.util.strtobool(some_string))

• Python 2: http://docs.python.org/2/distutils/apiref.html?highlight=distutils.util#distutils.util.strtobool
• Python >=3, <3.12: https://docs.python.org/3/distutils/apiref.html#distutils.util.strtobool
• Python >=3.12: No longer part of the standard library due to PEP 632

True values are y, yes, t, true, on and 1; false values are n, no, f, false, off and 0. Raises ValueError if val is anything else.

Be aware that distutils.util.strtobool() returns integer representations and thus it needs to be wrapped with bool() to get Boolean values.