How to use the re module for regular expression matching in Python 3.x

How to use the re module for regular expression matching in Python 3.x

Regular expression is a powerful text processing tool that can be used to match, find and replace specific patterns in strings . In Python, we can use the re module to perform regular expression matching operations.

First, we need to import the re module:

import re

Next, we can use the functions provided by the re module to match regular expressions.

1. re.match() function

re.match() function can start matching from the beginning of the string. If the match is successful, it returns a matching object. ; Otherwise, None is returned.

import re

pattern = r"hello"
string = "hello world"

result = re.match(pattern, string)

if result:
    print("匹配成功")
else:
    print("匹配失败")

The output result is:

匹配成功

2. re.search() function

re.search() function will search the entire character in the string string until the first match is found. If the match is successful, a matching object is returned; otherwise None is returned.

import re

pattern = r"world"
string = "hello world"

result = re.search(pattern, string)

if result:
    print("匹配成功")
else:
    print("匹配失败")

The output result is:

匹配成功

3. re.findall() function

The re.findall() function will search the entire character in the string string and returns a list of all matching items.

import re

pattern = r"o"
string = "hello world"

result = re.findall(pattern, string)

print(result)

The output result is:

['o', 'o', 'o']

4. re.split() function

re.split() function can match the regular expression to split a string and return a list of split strings.

import re

pattern = r"s+"
string = "hello        world"

result = re.split(pattern, string)

print(result)

The output result is:

['hello', 'world']

5. re.sub() function

re.sub() function is used to find and Replace matches.

import re

pattern = r"world"
string = "hello world"

result = re.sub(pattern, "universe", string)

print(result)

The output result is:

hello universe

The above are some common functions and examples of using the re module for regular expression matching. Through the flexible use of regular expressions, we can easily process and analyze text. I hope this article will help you learn and use regular expressions in Python.

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