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
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
def str2bool(v):
return v.lower() in ("yes", "true", "t", "1")
然后像这样称呼它:
>>> str2bool("yes")
True
>>> str2bool("no")
False
>>> str2bool("stuff")
False
>>> str2bool("1")
True
>>> str2bool("0")
False
显式处理true和false:
您还可以使函数显式地检查True单词列表和False单词列表。然后,如果它不在两个列表中,则可以抛出异常。
其他回答
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。
实际上,你只是将字符串与你期望接受的表示true的字符串进行比较,所以你可以这样做:
s == 'True'
或者检查一大堆值:
s.lower() in ['true', '1', 't', 'y', 'yes', 'yeah', 'yup', 'certainly', 'uh-huh']
使用以下物品时请谨慎:
>>> bool("foo")
True
>>> bool("")
False
空字符串的值是False,但其他的值都是True。所以这个不应该用于任何解析目的。
这是我的版本。它同时检查正值和负值列表,对于未知值引发异常。它不接收字符串,但任何类型都可以。
def to_bool(value):
"""
Converts 'something' to boolean. Raises exception for invalid formats
Possible True values: 1, True, "1", "TRue", "yes", "y", "t"
Possible False values: 0, False, None, [], {}, "", "0", "faLse", "no", "n", "f", 0.0, ...
"""
if str(value).lower() in ("yes", "y", "true", "t", "1"): return True
if str(value).lower() in ("no", "n", "false", "f", "0", "0.0", "", "none", "[]", "{}"): return False
raise Exception('Invalid value for boolean conversion: ' + str(value))
示例:
>>> to_bool(True)
True
>>> to_bool("tRUe")
True
>>> to_bool("1")
True
>>> to_bool(1)
True
>>> to_bool(2)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 9, in to_bool
Exception: Invalid value for boolean conversion: 2
>>> to_bool([])
False
>>> to_bool({})
False
>>> to_bool(None)
False
>>> to_bool("Wasssaaaaa")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 9, in to_bool
Exception: Invalid value for boolean conversion: Wasssaaaaa
>>>
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)
# ...
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),
]