python字符串反向输出

Python String doesn’t have a built-in reverse() function. However, there are various ways to reverse a string in Python.

Python String没有内置的reverse（）函数。 但是，有多种方法可以在Python中反转字符串。

1.如何在Python中反转字符串？ (1. How to Reverse a String in Python?)

Some of the common ways to reverse a string are:

反转字符串的一些常见方法是：

• Using Slicing to create a reverse copy of the string.

  使用切片来创建字符串的反向副本。

• Using for loop and appending characters in reverse order

  使用for循环并以相反顺序附加字符

• Using while loop to iterate string characters in reverse order and append them

  使用while循环以相反的顺序迭代字符串字符并追加它们

• Using string join() function with reversed() iterator

  在反向（）迭代器中使用字符串join（）函数

• Creating a list from the string and then calling its reverse() function

  从字符串创建列表 ，然后调用其reverse()函数

• Using Recursion

  使用递归

1.1）使用切片的Python反向字符串 (1.1) Python Reverse String using Slicing)

def reverse_slicing(s):
    return s[::-1]

input_str = 'ABç∂EF'

if __name__ == "__main__":
    print('Reverse String using slicing =', reverse_slicing(input_str))

If you run above Python script, the output will be:

如果您在Python脚本上运行，则输出将是：

Reverse String using slicing = FE∂çBA

1.2）使用For循环反向字符串 (1.2) Reverse String using For Loop)

def reverse_for_loop(s):
    s1 = ''
    for c in s:
        s1 = c + s1  # appending chars in reverse order
    return s1

input_str = 'ABç∂EF'

if __name__ == "__main__":
    print('Reverse String using for loop =', reverse_for_loop(input_str))

Output: Reverse String using for loop = FE∂çBA

输出： Reverse String using for loop = FE∂çBA

1.3）使用While循环反转字符串 (1.3) Reverse a String using While Loop)

def reverse_while_loop(s):
    s1 = ''
    length = len(s) - 1
    while length >= 0:
        s1 = s1 + s[length]
        length = length - 1
    return s1

input_str = 'ABç∂EF'

if __name__ == "__main__":
    print('Reverse String using while loop =', reverse_while_loop(input_str))

1.4）使用join（）和reversed（）反转字符串 (1.4) Reverse a String using join() and reversed())

def reverse_join_reversed_iter(s):
    s1 = ''.join(reversed(s))
    return s1

1.5）使用列表reverse（）的Python反向字符串 (1.5) Python Reverse String using List reverse())

def reverse_list(s):
    temp_list = list(s)
    temp_list.reverse()
    return ''.join(temp_list)

1.6）使用递归的Python反向字符串 (1.6) Python Reverse String using Recursion)

def reverse_recursion(s):
    if len(s) == 0:
        return s
    else:
        return reverse_recursion(s[1:]) + s[0]

2.用Python反转字符串的最佳方法 (2. Best Way to Reverse a String in Python)

We can reverse a string through multiple algorithms. We have already seen six of them. But which of them you should choose to reverse a string.

我们可以通过多种算法反转字符串。 我们已经看过其中的六个。 但是您应该选择其中的哪一个反向字符串。

We can use timeit module to run multiple iterations of these functions and get the average time required to run them.

我们可以使用timeit模块来运行这些函数的多次迭代，并获得运行它们所需的平均时间。

All the above functions are stored in a python script named string_reverse.py. I executed all these functions one by one for 1,00,000 times using the timeit module and got the average of the best 5 runs.

以上所有功能均存储在名为string_reverse.py的python脚本中。 我使用timeit模块一个接一个地执行了所有这些功能1,00,000次，并得到了最佳5次运行的平均值。

$ python3.7 -m timeit --number 100000 --unit usec 'import string_reverse' 'string_reverse.reverse_slicing("ABç∂EF"*10)'
100000 loops, best of 5: 0.449 usec per loop

$ python3.7 -m timeit --number 100000 --unit usec 'import string_reverse' 'string_reverse.reverse_list("ABç∂EF"*10)'
100000 loops, best of 5: 2.46 usec per loop

$ python3.7 -m timeit --number 100000 --unit usec 'import string_reverse' 'string_reverse.reverse_join_reversed_iter("ABç∂EF"*10)'
100000 loops, best of 5: 2.49 usec per loop

$ python3.7 -m timeit --number 100000 --unit usec 'import string_reverse' 'string_reverse.reverse_for_loop("ABç∂EF"*10)'
100000 loops, best of 5: 5.5 usec per loop

$ python3.7 -m timeit --number 100000 --unit usec 'import string_reverse' 'string_reverse.reverse_while_loop("ABç∂EF"*10)'
100000 loops, best of 5: 9.4 usec per loop

$ python3.7 -m timeit --number 100000 --unit usec 'import string_reverse' 'string_reverse.reverse_recursion("ABç∂EF"*10)'
100000 loops, best of 5: 24.3 usec per loop

The below table presents the results and slowness of an algorithm from the best one.

下表列出了最佳算法的结果和慢度。

3.总结 (3. Summary)

We should use slicing to reverse a string in Python. Its code is very simple and small and we don’t need to write our own logic to reverse the string. Also, it’s the fastest way to reverse a string as identified by the above test executions.

我们应该使用切片来反转Python中的字符串。 它的代码非常简单小巧，我们不需要编写自己的逻辑来反转字符串。 另外，这是反转上述测试执行所确定的字符串的最快方法。

GitHub Repository.
GitHub存储库中检出完整的python脚本和更多Python示例。

4.参考 (4. References)

• reversed() API Doc

  reversed（）API文档

• str.join() API Doc

  str.join（）API文档

翻译自: https://www.journaldev.com/23647/python-reverse-string

python字符串反向输出