python中False的判定与In

import json


def checkFalse(obj):
    if obj:
        print(f"{json.dumps(obj,ensure_ascii=False)}:True")
    else:
        print(f"{json.dumps(obj,ensure_ascii=False)}:False")


def checkExcuteFalse(script, obj):
    if obj:
        print(f"{script}:True")
    else:
        print(f"{script}:False")

checkFalse(None)
checkFalse({})
checkFalse([])
checkExcuteFalse("()",())
checkExcuteFalse("set()",set())
checkFalse("")
checkFalse(" ")
checkFalse('')
checkFalse(' ')
checkFalse(True)
checkFalse(False)
checkFalse(0)
checkFalse(0.0)
checkFalse(1)
checkFalse(-1)
checkExcuteFalse("1 in [1, 2]", 1 in [1, 2])
checkExcuteFalse("1 in [2]", 1 in [2])
checkExcuteFalse("1 in []", 1 in [])
checkExcuteFalse("1 in {'1': 5}", 1 in {"1": 5})
checkExcuteFalse("'1' in {'1': 5}", '1' in {"1": 5})
checkExcuteFalse("'a' in 'abc'", 'a' in 'abc')
checkExcuteFalse("1 in (1,'an')", 1 in (1,'an'))
checkExcuteFalse("[] in (1,[])", [] in (1,[]))
checkExcuteFalse("[1,2] in [1,2,3]", [1,2] in [1,2,3])
checkExcuteFalse("None in [None,2,3]", None in [None,2,3])
checkExcuteFalse("1 in set([1,2])", 1 in set([1,2]))

结果

null:False
{}:False
[]:False
():False
set():False
"":False
" ":True
"":False
" ":True
true:True
false:False
0:False
0.0:False
1:True
-1:True
1 in [1, 2]:True
1 in [2]:False
1 in []:False
1 in {'1': 5}:False
'1' in {'1': 5}:True
'a' in 'abc':True
1 in (1,'an'):True
[] in (1,[]):True
[1,2] in [1,2,3]:False
None in [None,2,3]:True
1 in set([1,2]):True

结论

一般意义上无效的数据，例如空字符串，空集合，空列表，空元组,None,空字典，数字0 都会被判定位Fasle
In 操作符 除了可以用来判定 字典的Key，还可以

1. 用于判断字符串中是否存在某个字符
2. 用于判断元组中是否存在某个元素
3. 用于判断列表中是否存在某个元素