Convert True/False value read from file to boolean

by

bool('True') and bool('False') always return True because strings ‘True’ and ‘False’ are not empty.

To quote a great man (and Python documentation):

5.1. Truth Value Testing

Any object can be tested for truth value, for use in an if or while
condition or as operand of the Boolean operations below. The
following values are considered false:

  • …
  • zero of any numeric type, for example, 0, 0L, 0.0, 0j.
  • any empty sequence, for example, '', (), [].
  • …

All other values are considered true — so objects of many types
are always true.

The built-in bool function uses the standard truth testing procedure. That’s why you’re always getting True.

To convert a string to boolean you need to do something like this:

def str_to_bool(s):
    if s == 'True':
         return True
    elif s == 'False':
         return False
    else:
         raise ValueError # evil ValueError that doesn't tell you what the wrong value was

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