How to use regular expressions for pattern matching in Python

Regular expression is a powerful text matching tool, you can use the re module in python Perform pattern matching. The following are the general steps for pattern matching using regular expressions:

1. Import the re module: First, you need to import the re module, using the import re statement.

2. Create a regular expression: Use the compile() function of the re module to create a regular expression object. A regular expression is a special string that defines a pattern to match.

For example, we can use the following code to create a regular expression object that matches mobile phone numbers:

<code>import re
pattern = re.compile(r'^1[3456789]\d{9}$')</code>

This regular expression can match a string that starts with 1 and is followed by 10 digits.

3. Match: Use the match() or search() function of the regular expression object to match. The difference between these two functions is that the match() function will only match from the beginning of the string, while the search() function will search the entire string.

For example, we can use the following code to match:

<code>result = pattern.match('13812345678')</code>

If the match is successful, a matching object will be returned; if it is unsuccessful, None will be returned.

4. Extract matching results: You can use the group() method of the matching object to obtain the matching results.

For example, we can use the following code to extract the matching results:

<code>if result:
    print(result.group())</code>

This code will print out the matching mobile phone number.

In addition to the match() and search() functions, the re module also provides other functions for pattern matching, such as findall(), finditer(), sub(), etc.

Summary:

To use regular expressions for pattern matching, you need to import the re module, create a regular expression object, and use the match() or search() function. match. Matching results can be extracted through the group() method of the matching object. Regular expressions are a powerful text matching tool capable of efficient pattern matching and extraction.

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