如何在Python中将字符串转换为布尔值?这个尝试返回True:

>>> bool("False")
True

当前回答

在python 3.10版本中,你可以这样做;

def stringToBool(string: str) -> bool:
    match(string.lower()):
        case 'true':
            return True
        case 'false':
            return False

match-statement等价于c++中的switch。

其他回答

从Python 2.6开始,你可以使用ast.literal_eval:

>>> import ast
>>> help(ast.literal_eval)
Help on function literal_eval in module ast:

literal_eval(node_or_string)
    Safely evaluate an expression node or a string containing a Python
    expression.  The string or node provided may only consist of the following
    Python literal structures: strings, numbers, tuples, lists, dicts, booleans,
    and None.

这似乎是可行的,只要你确定你的字符串将是“True”或“False”:

>>> ast.literal_eval("True")
True
>>> ast.literal_eval("False")
False
>>> ast.literal_eval("F")
Traceback (most recent call last):
  File "", line 1, in 
  File "/opt/Python-2.6.1/lib/python2.6/ast.py", line 68, in literal_eval
    return _convert(node_or_string)
  File "/opt/Python-2.6.1/lib/python2.6/ast.py", line 67, in _convert
    raise ValueError('malformed string')
ValueError: malformed string
>>> ast.literal_eval("'False'")
'False'

我通常不建议这样做,但它是完全内置的,可以根据您的需求来选择。

下面是我用来评估字符串真实性的东西:

def as_bool(val):
 if val:
  try:
   if not int(val): val=False
  except: pass
  try:
   if val.lower()=="false": val=False
  except: pass
 return bool(val)

与使用eval的结果大致相同,但更安全。

通过使用Python内置的eval()函数和.capitalize()方法,您可以将任何“true”/“false”字符串(不管初始大写)转换为true Python布尔值。

例如:

true_false = "trUE"
type(true_false)

# OUTPUT: <type 'str'>

true_false = eval(true_false.capitalize())
type(true_false)

# OUTPUT: <type 'bool'>

该版本保留了int(value)等构造函数的语义,并提供了一种简单的方法来定义可接受的字符串值。

def to_bool(value):
    valid = {'true': True, 't': True, '1': True,
             'false': False, 'f': False, '0': False,
             }   

    if isinstance(value, bool):
        return value

    if not isinstance(value, basestring):
        raise ValueError('invalid literal for boolean. Not a string.')

    lower_value = value.lower()
    if lower_value in valid:
        return valid[lower_value]
    else:
        raise ValueError('invalid literal for boolean: "%s"' % value)


# Test cases
assert to_bool('true'), '"true" is True' 
assert to_bool('True'), '"True" is True' 
assert to_bool('TRue'), '"TRue" is True' 
assert to_bool('TRUE'), '"TRUE" is True' 
assert to_bool('T'), '"T" is True' 
assert to_bool('t'), '"t" is True' 
assert to_bool('1'), '"1" is True' 
assert to_bool(True), 'True is True' 
assert to_bool(u'true'), 'unicode "true" is True'

assert to_bool('false') is False, '"false" is False' 
assert to_bool('False') is False, '"False" is False' 
assert to_bool('FAlse') is False, '"FAlse" is False' 
assert to_bool('FALSE') is False, '"FALSE" is False' 
assert to_bool('F') is False, '"F" is False' 
assert to_bool('f') is False, '"f" is False' 
assert to_bool('0') is False, '"0" is False' 
assert to_bool(False) is False, 'False is False'
assert to_bool(u'false') is False, 'unicode "false" is False'

# Expect ValueError to be raised for invalid parameter...
try:
    to_bool('')
    to_bool(12)
    to_bool([])
    to_bool('yes')
    to_bool('FOObar')
except ValueError, e:
    pass

JSON解析器在将字符串转换为合理的python类型时也很有用。

>>> import json
>>> json.loads("false".lower())
False
>>> json.loads("True".lower())
True