len函数python

Python len() function returns the length of the object. Generally, len() function is used with sequences (string, tuple) and collections (dict, set) 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， 元组 ）和集合（ dict ， set ）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 sequence
print('string length =', len('abc'))  # string
print('tuple length =', len((1, 2, 3)))  # tuple
print('list length =', len([1, 2, 3, 4]))  # list
print('bytes length =', len(bytes('abc', 'utf-8')))  # bytes
print('range length =', len(range(10, 20, 2)))  # range# len with collections
print('dict length =', len({"a": 1, "b": 2}))  # dict
print('set length =', len(set([1, 2, 3, 3])))  # set
print('frozenset length =', len(frozenset([1, 2, 2, 3])))  # frozenset

Output:

输出：

string length = 3
tuple length = 3
list length = 4
bytes length = 3
range length = 5
dict length = 2
set length = 3
frozenset 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 = ndef __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: Official Documentation

参考： 官方文档

翻译自: https://www.journaldev.com/22942/python-len-function

len函数python