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

这是我写的版本。将其他几个解决方案合并为一个。

def to_bool(value):
    """
    Converts 'something' to boolean. Raises exception if it gets a string it doesn't handle.
    Case is ignored for strings. These string values are handled:
      True: 'True', "1", "TRue", "yes", "y", "t"
      False: "", "0", "faLse", "no", "n", "f"
    Non-string values are passed to bool.
    """
    if type(value) == type(''):
        if value.lower() in ("yes", "y", "true",  "t", "1"):
            return True
        if value.lower() in ("no",  "n", "false", "f", "0", ""):
            return False
        raise Exception('Invalid value for boolean conversion: ' + value)
    return bool(value)

如果它得到一个字符串，它期望特定的值，否则引发异常。如果它没有得到一个字符串，就让bool构造函数来计算它。测试这些案例:

test_cases = [
    ('true', True),
    ('t', True),
    ('yes', True),
    ('y', True),
    ('1', True),
    ('false', False),
    ('f', False),
    ('no', False),
    ('n', False),
    ('0', False),
    ('', False),
    (1, True),
    (0, False),
    (1.0, True),
    (0.0, False),
    ([], False),
    ({}, False),
    ((), False),
    ([1], True),
    ({1:2}, True),
    ((1,), True),
    (None, False),
    (object(), True),
    ]

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。

如果你可以控制返回true/false的实体，一种选择是让它返回1/0而不是true/false，那么:

boolean = bool(int(response))

额外的转换为int处理来自网络的响应，这些响应总是字符串。

2021年更新:“which are always string”——这是一个幼稚的观察。它取决于库使用的序列化协议。高级库(大多数web开发人员使用的库)的默认序列化通常是在序列化为字节之前转换为字符串。然后在另一边，它从字节反序列化为字符串，所以你丢失了任何类型信息。

我还被要求将一个函数的输入更改为bool，主要输入在字符串中仅为True或False。所以，我只是这样编码:

def string_to_bool(s):
    bool_flag = True
    if s == "False":
        bool_flag = False
    elif s == "True":
        bool_flag = True
    else:
        print("Invalid Input")
    return bool_flag

你也可以检查它是否有更短的真假，如Y/N或Y/N等。

这个答案使用了Django Rest Framework (DRF) 3.14中的代码。

你可以:

from rest_framework.fields import BooleanField
f = BooleanField(allow_null=True)
test_values = [ True, "True", "1", 1, -1, 1.0, "true", "t", "on",
         None, "null", "NULL",
         False, "False", "0", 0, "false", "f", 0.0, "off" ]
for item in test_values:
    r = f.to_internal_value(item)
    print(r)
   
# a shorter version
from rest_framework.fields import BooleanField
test_values = [ True, "True", "1", 1, -1, 1.0, "true", "t", "on",
         None, "null", "NULL",
         False, "False", "0", 0, "false", "f", 0.0, "off" ]
for item in test_values:
    print(BooleanField(allow_null=True).to_internal_value(item))

或者您可以调整BooleanField的代码，使其适合您的需要。下面是DRF 3.x中类BooleanField的实际代码

# from rest_framework.fields 
# ...

class BooleanField(Field):
    default_error_messages = {
        'invalid': _('Must be a valid boolean.')
    }
    default_empty_html = False
    initial = False
    TRUE_VALUES = {
        't', 'T',
        'y', 'Y', 'yes', 'Yes', 'YES',
        'true', 'True', 'TRUE',
        'on', 'On', 'ON',
        '1', 1,
        True
    }
    FALSE_VALUES = {
        'f', 'F',
        'n', 'N', 'no', 'No', 'NO',
        'false', 'False', 'FALSE',
        'off', 'Off', 'OFF',
        '0', 0, 0.0,
        False
    }
    NULL_VALUES = {'null', 'Null', 'NULL', '', None}
    
    def to_internal_value(self, data):
        try:
            if data in self.TRUE_VALUES:
                return True
            elif data in self.FALSE_VALUES:
                return False
            elif data in self.NULL_VALUES and self.allow_null:
                return None
        except TypeError:  # Input is an unhashable type
            pass
        self.fail('invalid', input=data)
    
    def to_representation(self, value):
        if value in self.TRUE_VALUES:
            return True
        elif value in self.FALSE_VALUES:
            return False
        if value in self.NULL_VALUES and self.allow_null:
            return None
        return bool(value)

# ...