Python built-in function len

English documents:

Len (s)

Return the length (the number of items) of an object. The argument may is a sequence (such as a string, bytes, tuple, list, or range) or a collection (such as a dictionary, set , or frozen set).

Description

1. Returns the length of an object, which can be a sequence (such as a string, byte array, tuple, list, and Range object), or a collection (such as a dictionary, collection, immutable collection)

>>> len (' ABCD ') # string >>> len (bytes (' ABCD ', ' Utf-8 ')) # byte array >>> len ((1,2,3,4)) # tuple >> > len ([1,2,3,4]) # list >>> len (range 1,5) # Range object >>> len ({' A ': 1, ' B ': 2, ' C ': 3, ' d ': 4}) # dictionary >>& Gt Len ({' A ', ' B ', ' C ', ' d '}) # collection >>> len (Frozenset (' ABCD ')) #不可变集合

2. If the parameter is a different type, it must implement the __len__ method and return an integer, otherwise an error.

>>> class A:    def __init__ (self,name):        self.name = name    def __len__ (self):        return Len ( Self.name) >>> a = A (") >>> Len (a) >>> a = A (' Aim ') >>> Len (a) >>> class B:    pass>>> B = B () >>> Len (b) Traceback (most recent call last):  File "
 
  
   
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       len (b) Typeerror:object of type ' B ' have no Len () >>> class C:
    def __len__ (self):        return ' len ' >>> C = C () >>> Len (c) Traceback (most recent call last):  File "
   
    
     
    ", line 1, in 
    
     
      
         len (c) TypeError: ' str ' object cannot is interpreted as an INTEGER
      
     
   
    
  
   
 
  

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