python中鲜为人知的功能特性有哪些

python中鲜为人知的功能特性有哪些

本篇内容主要讲解“python中鲜为人知的功能特性有哪些”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“python中鲜为人知的功能特性有哪些”吧!

微妙的字符串

>>> a = "wtf"
>>> b = "wtf"
>>> a is b
True

>>> a = "wtf!"
>>> b = "wtf!"
>>> a is b
False

>>> a, b = "wtf!", "wtf!"
>>> a is b
True # 3.7 版本返回结果为 False.

出乎意料的”is”

>>> a = 256
>>> b = 256
>>> a is b
True

>>> a = 257
>>> b = 257
>>> a is b
False

>>> a = 257; b = 257
>>> a is b
True

说好的元组不可变呢

some_tuple = ("A", "tuple", "with", "values")
another_tuple = ([1, 2], [3, 4], [5, 6])

>>> some_tuple[2] = "change this"
TypeError: 'tuple' object does not support item assignment
>>> another_tuple[2].append(1000) # 这里不出现错误
>>> another_tuple
([1, 2], [3, 4], [5, 6, 1000])
>>> another_tuple[2] += [99, 999]
TypeError: 'tuple' object does not support item assignment
>>> another_tuple
([1, 2], [3, 4], [5, 6, 1000, 99, 999])

消失的全局变量

e = 7
try:
raise Exception()
except Exception as e:
pass

输出

>>> print(e)
NameError: name 'e' is not defined

try 遇到 finally到底返回哪个值

def some_func():
try:
return 'from_try'
finally:
return 'from_finally'

输出

>>> some_func()
'from_finally'

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