python中那些不爲人知的功能特性

常常逛GitHub的可能關注一個牛叉的項目，叫 What the f*ck Python!

這個項目列出了幾乎全部python中那些不爲人知的功能特性，有些功能第一次碰見時，你會冒出 what the f**k 的感嘆。

由於這些例子看起來反人類直覺。

可是若是你理解了它背後的真正原理，你又會驚歎what the f**k， 居然還有這麼騷的操做。

來看看幾個例子吧。

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 版本返回結果爲 False.
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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
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說好的元組不可變呢

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) # 這裏不出現錯誤
>>> 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])
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消失的全局變量

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

>>> print(e)
NameError: name 'e' is not defined
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到底返回哪一個值

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

>>> some_func()
'from_finally'
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諸如此類的例子一共有50多個

若是你能把這50多個特性背後的原理機制所有了解清楚，我相信你的python功力必定會上升一個層次。

傳送門: github.com/leisurelich…

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