Use regular expression functions to easily match text

Regular expressions are a powerful text matching tool that can be used in different programming languages ​​or text editors. In text processing, regular expression functions allow us to easily match and filter text content and improve text processing efficiency.

Regular expression functions usually have some basic metacharacters and symbols, such as:

• . (dot): matches any single character;
• ^( Caret): matches the beginning of the line;
• $ (dollar sign): matches the end of the line;
• [] (character set): matches any character in the character set;
• d: matches numbers;
• w: matches letters or numbers or underscores;
• s: matches whitespace characters such as spaces or tabs.

The following introduces some examples of practical application of regular expression functions.

1. Extract phone numbers from a text

If there is a text that contains multiple phone numbers, like this:

This is mine The phone number is 123-456-7890, and the other phone number is 111-222-3333.

We can use the regular expression function to extract these phone numbers. The code is as follows:

import re

text = "这是我的电话号码 123-456-7890，另外一个电话号码是 111-222-3333。"
pattern = r"d{3}-d{3}-d{4}"
phone_numbers = re.findall(pattern, text)

print(phone_numbers)

In the above code, Python's regular expression library re is first imported. Then a variable text is defined and assigned the text content containing the phone number. Next, a regular expression pattern is defined, d{3}-d{3}-d{4} means matching the phone number format in the form xxx-xxx-xxxx. Finally, use the re.findall function to find all phone numbers matching the pattern and store the matching results in the variable phone_numbers. Running the above code, the output result is ['123-456-7890', '111-222-3333'].

2. Determine whether a piece of text conforms to the email address format

Email addresses usually contain the format username@domain, where username is the user name and domain is the domain name of the mail server . Here is an example to determine whether the email address format is correct:

import re

text = "我的邮箱是john@example.com。"
pattern = r"w+@w+.w+"
if re.search(pattern, text):
    print(text + " 是一个有效的邮箱地址。")
else:
    print(text + " 不是一个有效的邮箱地址。")

In the above code, use the re.search function to find text content that matches the email address format. The regular expression pattern w @w .w is used to match email addresses that meet the format requirements. If text content that meets the criteria is found, the specified text content is output to be a valid email address.

Using regular expression functions can greatly improve the efficiency and accuracy of text processing. However, it should be noted that the regular expression function may be affected by text encoding, language habits and other factors, so it needs to be adjusted and optimized based on the specific situation when used.

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