Utilisation et exemple de reversed() en Python

Built-in functions in Python

La fonction reversed() retourne un itérateur inversé de la séquence donnée.

La syntaxe de reversed() est :

reversed(seq)

Paramètre de reversed()

La fonction reversed() utilise un seul paramètre :

• seq -L'ordre à inverser

A sequence is an object that supports the sequence protocol __len__() and __getitem__() methods. For example,tuple,string,list,rangeetc.

We can also use reversed() on any object that implements __reverse__().

reversed() return value

The reversed() function returns an iterator that accesses the given sequence in reverse order.

Example1: Using reversed() in strings, tuples, lists, and ranges

# For string
seq_string = 'Python'
print(list(reversed(seq_string)))
# For tuple
seq_tuple = ('P', 'y', 't', 'h', 'o', 'n')
print(list(reversed(seq_tuple)))
# For range
seq_range = range(5,　9)
print(list(reversed(seq_range)))
# For list
seq_list = [1,　2,　4,　3,　5]
print(list(reversed(seq_list)))

Output result

['n', 'o', 'h', 't', 'y', 'P']
['n', 'o', 'h', 't', 'y', 'P']
[8,　7,　6,　5]
[5,　3,　4,　2,　1]

In our example, we use the list() function to convert the iterator returned by reverse() to a list.

Example2: Custom object's reversed()

class Vowels:
　　　　vowels = ['a', 'e', 'i', 'o', 'u']
　　　　def __reversed__(self):
　　　　　　　　return reversed(self.vowels)
v = Vowels()
print(list(reversed(v)))

Output result

['u', 'o', 'i', 'e', 'a']

Built-in functions in Python