len函数python

Python len() function returns the length of the object. Generally, len() function is used with sequences (string, ) and collections (, ) to get the number of items.

Python len（）函数返回对象的长度。 通常，len（）函数与序列（字符串， ）和集合（ ， ）一起使用以获取项数。

Python len（）函数 (Python len() function)

Python len() function returns the length of the object. This function internally calls __len__() function of the object. So we can use len() function with any object that defines __len__() function.

Python len（）函数返回对象的长度。 此函数在内部调用对象的__len __（）函数。 因此，我们可以将len（）函数与任何定义__len __（）函数的对象一起使用。

Let’s look at some examples of using len() function with built-in sequences and collection objects.

让我们看一些将len（）函数与内置序列和集合对象一起使用的示例。

# len with sequenceprint('string length =', len('abc'))  # stringprint('tuple length =', len((1, 2, 3)))  # tupleprint('list length =', len([1, 2, 3, 4]))  # listprint('bytes length =', len(bytes('abc', 'utf-8')))  # bytesprint('range length =', len(range(10, 20, 2)))  # range# len with collectionsprint('dict length =', len({"a": 1, "b": 2}))  # dictprint('set length =', len(set([1, 2, 3, 3])))  # setprint('frozenset length =', len(frozenset([1, 2, 2, 3])))  # frozenset

Output:

输出：

string length = 3tuple length = 3list length = 4bytes length = 3range length = 5dict length = 2set length = 3frozenset length = 3

Python len（）对象 (Python len() Object)

Let’s define a custom class with __len__() function and call len() function with it’s object as argument.

让我们使用__len __（）函数定义一个自定义类，并以其对象作为参数调用len（）函数。

class Employee:    name = ''    def __init__(self, n):        self.name = n    def __len__(self):        return len(self.name)e = Employee('Pankaj')print('employee object length =', len(e))

Output:

输出：

employee object length = 6

If we remove __len__() function from Employee object, we will get the following exception.

如果我们从Employee对象中删除__len __（）函数，我们将得到以下异常。

TypeError: object of type 'Employee' has no len()

Reference:

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len函数python