Uso y ejemplo de len() en Python

Python built-in functions

La funcixf3n len() devuelve el nxfamero de elementos o la longitud de un objeto.

Sintaxis de len():

len(s)

Parxe1metros de len()

s-Secuencias (cadenas, bytes, tuplas, listas o rangos) o conjuntos (diccionarios, conjuntos o conjuntos congelados)

Retorno de len()

La funcixf3n len() devuelve el nxfamero de elementos de un objeto.

xe4xb8xb4xe8xbfx87xe5x8fx82xe6x95xb0xe6x88x96xe4xb8x8dxe4xbdxb5xe6x95xb0xe6x8dxaexe5x8fx82xe6x95xb0xe5xa4x9axe6x89xa7xe8xa1x8cTypeErrorxefxbcx8c

Example1¿xe5xa6x82xe4xb9x94xe4xb8xbaxe5xadx97xe8xa1x8cxe5xafx86xe7x89xa9，xe5x88x97xe8xa1xa8x5fxb5x94xe5x9fxbax5fxe7x94xa8xe6xb3x95?

xe6xb5x8cx8aList xe4xb8x8dx5b []
print(xe6xb5x8cx8aList, '项目个数为', xe9x95x9cxe5xb0x9a(len(xe6xb5x8cx8aList)))
xe6xb5x8cx8aList xe4xb8x8dx5b [1,　2,　3]
print(xe6xb5x8cx8aList, '项目个数为', xe9x95x9cxe5xb0x9a(len(xe6xb5x8cx8aList)))
xe6xb5x8cx8aTuple xe4xb8x8dx5b (1,　2,　3)
print(xe6xb5x8cx8aTuple, '项目个数为', xe9x95x9cxe5xb0x9a(len(xe6xb5x8cx8aTuple)))
xe6xb5x8cx8aRange xe4xb8x8dx5b range(1,　10)
print('Proyecto', xe6xb5x8cx8aRange, '个数为', xe9x95x9cxe5xb0x9a(len(xe6xb5x8cx8aRange)))

When running the program, the output is:

[] xe6x9cx89xe4xb8x80xe7x82xb9xe6x95xb0 xe6x98xaf xe5x8fxafxe7x82xb9
[1,　2,　3] xe6x9cx89xe4xb8x80xe7x82xb9xe6x95xb0　3
(1,　2,　3) xe6x9cx89xe4xb8x80xe7x82xb9xe6x95xb0　3
Proyecto range(1,　10) xe6x9cx89xe4xb8x80xe7x82xb9xe6x95xb0　9

Visit these pages to learn more about the following content:

• Lista de Python

• Python tuple

• Mx65todo range() de Python

Example2¿xe5xa6x82xe4xb9x94xe5xa4x84xe7x90x86xe6x9cxacxe5xadx97xe5x92x8cxe5xadx97xe8xa1x8cxe5xafx86xe7x89xa9?

xe6xb5x8cx8aString xe4xb8x8dx5b ''
print('Cadena', xe6xb5x8cx8aString, '长度是', xe9x95x9cxe5xb0x9a(len(xe6xb5x8cx8aString)))
xe6xb5x8cx8aString xe4xb8x8dx5b 'Python'
print('Cadena', xe6xb5x8cx8aString, '长度是', xe9x95x9cxe5xb0x9a(len(xe6xb5x8cx8aString)))
# xe5xadx97xe8xa1x8cxe5xafx86xe7x89xa9
xe6xb5x8cx8aByte xe4xb8x8dx5b xb5'Python'
print('Cadena', xe6xb5x8cx8aByte, '长度是', xe9x95x9cxe5xb0x9a(len(xe6xb5x8cx8aByte)))
xe6xb5x8cx8aList xe4xb8x8dx5b [1,　2,　3]
# xe8xb7x9fxe8xbdxacxe4xb8xbaxe5xadx97xe8xa1x8cxe5xafx86xe7x89xa9
xe6xb5x8cx8aByte xe4xb8x8dx5b xe5xb0x9cx8a(bytes(xe6xb5x8cx8aList))
print('Cadena', xe6xb5x8cx8aByte, '长度是', xe9x95x9cxe5xb0x9a(len(xe6xb5x8cx8aByte)))

When running the program, the output is:

Cadena xe7xa9xba xe9x95x9cxe5xb0x9axe6x98xaf xe5x8fxafxe7x82xb9
Cadena Python xe9x95x9cxe5xb0x9axe6x98xaf　6
Cadena xb5'Python' xe9x95x9cxe5xb0x9axe6x98xaf　6
Cadena xb5'\x0123Length is '　长度是'　3

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• Python string

• Python bytes() method

Example3：How to use len() with dictionaries and sets?

testSet = {1,　2,　3}
print(testSet, 'Length is', len(testSet))
# Empty Set
testSet = set()
print(testSet, 'Length is', len(testSet))
testDict = {1: 'one',　2: 'two'}
print(testDict, 'Length is', len(testDict))
testDict = {}
print(testDict, 'Length is', len(testDict))
testSet = {1,　2}
# frozenSet
frozenTestSet = frozenset(testSet)
print(frozenTestSet, 'Length is', len(frozenTestSet))

When running the program, the output is:

{1,　2,　3} Length is　3
set() Length is 0
{1: 'one',　2: 'two' Length is　2
{} Length is 0
frozenset({1,　2}) Length is　2

Visit these pages to learn more about the following content:

• Python dictionary

• Python set

• Python Frozenset()

Internally, len() calls the object's __len__ method. You can understand len() as:

def len(s):
　　　　return s.__len__()

Therefore, you can assign a custom length to the object (if necessary)

Example4：How to use len() for custom objects?

class Session:
　　　　def __init__(self, number = 0):
　　　　　　self.number = number
　　　　
　　　　def __len__(self):
　　　　　　return self.number
# Default length is 0
s1　= Session()
print(len(s1))
# Given length
s2　= Session(6)
print(len(s2))

When running the program, the output is:

0
6

Python built-in functions