1) bool类是从int类继承而来的
2) True/False 在python2中不是关键字，但是在python3是(True,False,None)
PS > python2
Enthought Canopy Python 2.7.11 | 64-bit | (default, Jun 11 2016, 11:33:47) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import keyword
>>> keyword.kwlist
['and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'exec', 'finally', 'for',
'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'print', 'raise', 'return', 'try', 'while',
'with', 'yield']
>>> PS > python3
Python 3.5.2 (v3.5.2:4def2a2901a5, Jun 25 2016, 22:01:18) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import keyword
>>> keyword.kwlist
['False', 'None', 'True', 'and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', '
finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'retu
rn', 'try', 'while', 'with', 'yield']
>>>
由于Python2中True/False不是关键字，因此我们可以对其进行任意的赋值
>>> True="test"
>>> True
'test'
>>> "test"==True
True
>>> 1==True
False
>>>
3) 由于bool是继承自int的子类，因此为了保证向下兼容性，在进行算术运算中，True/False会被当作int值来执行
>>> del True
>>> True+True
2
>>> False + False
0
>>>
4)While 1 比While True快
import timeit def while_one():
i=0
while 1:
i+=1
if i==10000000:
break def while_true():
i=0
while True:
i+=1
if i==10000000:
break if __name__=="__main__":
t1=timeit.timeit(while_one,"from __main__ import while_one",number=3)
t2=timeit.timeit(while_true,"from __main__ import while_true", number=3)
#t1=timeit.timeit(while_one,"from __main__ import while_one",number=3)
print "while one : %s \nwhile true: %s " % (t1,t2) while one : 1.16112167105
while true: 1.66502957924
原因就是前提中提到的关键字的问题。由于Python2中，True/False不是关键字，因此我们可以对其进行任意的赋值，这就导致程序在每次循环时都需要对True/False的值进行检查；而对于1，则被程序进行了优化，而后不会再进行检查。
我们可以通过dis模块来查看while_one和while_true的字节码
import dis def while_one():
while 1:
pass def while_true():
while True:
pass if __name__=="__main__":
print "while_one \n"
dis.dis(while_one) print "while_true \n"
dis.dis(while_true)
结果：
while_one 4 0 SETUP_LOOP 4 (to 7) 5 >> 3 JUMP_ABSOLUTE 3
6 POP_BLOCK
>> 7 LOAD_CONST 0 (None)
10 RETURN_VALUE
while_true 8 0 SETUP_LOOP 10 (to 13)
>> 3 LOAD_GLOBAL 0 (True)
6 POP_JUMP_IF_FALSE 12 9 9 JUMP_ABSOLUTE 3
>> 12 POP_BLOCK
>> 13 LOAD_CONST 0 (None)
16 RETURN_VALUE
可以看出，正如上面所讲到的，在while True的时候，字节码中多出了几行语句，正是这几行语句进行了True值的检查
而在Python3中，由于True/False已经是关键字了，不允许进行重新赋值，因此，其执行结果与while 1不再有区别
PS > python3
Python 3.5.2 (v3.5.2:4def2a2901a5, Jun 25 2016, 22:01:18) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from test_while import *
>>> t1=timeit.timeit(while_one,"from __main__ import while_one",number=3)
>>> t2=timeit.timeit(while_true,"from __main__ import while_true", number=3)
>>> t1
3.1002996925072743
>>> t2
3.077654023474544
5) if x==True or if x:
后者比前者快
#! python2
#-*- coding:utf-8 -*- import timeit def if_x_eq_true():
x=True
if x==True:
pass def if_x():
x=True
if x:
pass if __name__=="__main__":
t1=timeit.timeit(if_x_eq_true,"from __main__ import if_x_eq_true", number=1000000)
t2=timeit.timeit(if_x,"from __main__ import if_x",number=1000000)
print "if_x_eq_true: %s \n if_x: %s" % (t1,t2) if_x_eq_true: 0.186029813246
if_x: 0.120894725822
字节码：
import dis def if_x_eq_true():
x=True
if x==True:
pass def if_x():
x=True
if x:
pass if __name__=="__main__":
print "if_x_eq_true \n"
dis.dis(if_x_eq_true) print "if_x \n"
dis.dis(if_x)
结果
if_x_eq_true 4 0 LOAD_GLOBAL 0 (True)
3 STORE_FAST 0 (x) 5 6 LOAD_FAST 0 (x)
9 LOAD_GLOBAL 0 (True)
12 COMPARE_OP 2 (==)
15 POP_JUMP_IF_FALSE 21 6 18 JUMP_FORWARD 0 (to 21)
>> 21 LOAD_CONST 0 (None)
24 RETURN_VALUE
if_x 9 0 LOAD_GLOBAL 0 (True)
3 STORE_FAST 0 (x) 10 6 LOAD_FAST 0 (x)
9 POP_JUMP_IF_FALSE 15 11 12 JUMP_FORWARD 0 (to 15)
>> 15 LOAD_CONST 0 (None)
18 RETURN_VALUE