python 字符串子串

python 字符串子串

A substring is the part of a string. Python string provides various methods to create a substring, check if it contains a substring, index of substring etc. In this tutorial, we will look into various operations related to substrings.

子字符串是字符串的一部分。 Python字符串提供了各种方法来创建子字符串，检查其是否包含子字符串，子字符串的索引等。在本教程中，我们将研究与子字符串相关的各种操作。

Python字符串子字符串 (Python String Substring)

Let’s first look at two different ways to create a substring.

首先让我们看一下创建子字符串的两种不同方法。

创建一个子串 (Create a Substring)

We can create a substring using string slicing. We can use split() function to create a list of substrings based on specified delimiter.

我们可以使用字符串切片来创建子字符串 。 我们可以使用split（）函数根据指定的分隔符创建子字符串列表。

s = 'My Name is Pankaj'

# create substring using slice
name = s[11:]
print(name)

# list of substrings using split
l1 = s.split()
print(l1)

Output:

输出：

Pankaj
['My', 'Name', 'is', 'Pankaj']

检查是否找到子字符串 (Checking if substring is found)

We can use in operator or find() function to check if substring is present in the string or not.

我们可以使用in运算符或find（）函数来检查字符串中是否存在子字符串。

s = 'My Name is Pankaj'

if 'Name' in s:
    print('Substring found')

if s.find('Name') != -1:
    print('Substring found')

Note that find() function returns the index position of the substring if it’s found, otherwise it returns -1.

注意，find（）函数返回子字符串的索引位置（如果找到），否则返回-1。

子字符串出现次数 (Count of Substring Occurrence)

We can use count() function to find the number of occurrences of a substring in the string.

我们可以使用count（）函数查找字符串中子字符串的出现次数。

s = 'My Name is Pankaj'

print('Substring count =', s.count('a'))

s = 'This Is The Best Theorem'
print('Substring count =', s.count('Th'))

Output:

输出：

Substring count = 3
Substring count = 3

查找子字符串的所有索引 (Find all indexes of substring)

There is no built-in function to get the list of all the indexes for the substring. However, we can easily define one using find() function.

没有内置函数来获取子字符串的所有索引的列表。 但是，我们可以使用find（）函数轻松定义一个。

def find_all_indexes(input_str, substring):
    l2 = []
    length = len(input_str)
    index = 0
    while index < length:
        i = input_str.find(substring, index)
        if i == -1:
            return l2
        l2.append(i)
        index = i + 1
    return l2


s = 'This Is The Best Theorem'
print(find_all_indexes(s, 'Th'))

Output: [0, 8, 17]

输出： [0, 8, 17]

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

翻译自: https://www.journaldev.com/23774/python-string-substring

python 字符串子串