Python內建bin函數詳細介紹

英文文檔：

bin(x)

Convert an integer number to a binary string. The result is a valid Python expression. If x is not a Python int object, it has to define an __index__() method that returns an integer.

說明：

1. 將一個整形數字轉換成二進位字串

>>> b = bin(3) >>> b'0b11'>>> type(b) #擷取b的類型<class 'str'>

2. 如果參數x不是一個整數，則x必須定義一個 __index__() 方法，並且方法傳回值必須是整數。

2.1 如果對象不是整數，則報錯

>>> class A:    pass>>> a = A()>>> bin(a) Traceback (most recent call last):  File "<pyshell#15>", line 1, in <module>    bin(a)TypeError: 'A' object cannot be interpreted as an integer

2.2 如果對象定義了__index__方法，但傳回值不是整數，報錯

>>> class B:    def __index__(self):        return "3">>> b = B()>>> bin(b)Traceback (most recent call last):  File "<pyshell#21>", line 1, in <module>    bin(b)TypeError: __index__ returned non-int (type str)

2.3 對象定義了__index__方法，且傳回值是整數，將__index__方法傳回值轉換成二進位字串

>>> class C:    def __index__(self):        return 3>>> c = C()>>> bin(c)'0b11'