How to use Python regular expressions to match Chinese and English mixed strings

Regular expression is a powerful text processing tool that can help us quickly match and replace strings. In the scenario of mixed Chinese and English string matching, the use of regular expressions is particularly important. This article will introduce how to use Python regular expressions to match Chinese and English mixed strings.

1. String encoding issues

Before matching Chinese and English mixed strings, you need to understand the string encoding issues first. In the Python 3.x version, strings use Unicode encoding by default, which means that a character is usually represented by a Unicode encoding in Python.

In practical applications, due to historical reasons and technical limitations, we often encounter strings of other encoding types. For example, the string encoding used in the Chinese environment is usually GBK or UTF-8. In order to correctly handle strings of different encodings, the strings need to be converted to a unified encoding before using regular expressions.

In Python, you can use the encode() method to convert a string into a byte string with a specified encoding, for example:

str = "中文字符串"
encoded_str = str.encode('utf-8')

2. Basic regular expression syntax

When using regular expressions to match mixed Chinese and English strings, you need to master some basic regular expression syntax.

1. Character class[]

The square brackets can match any of the characters, for example:

[abc]  匹配字符a或b或c
[a-z]  匹配小写字母a~z中的任意一个字符
[A-Z]  匹配大写字母A~Z中的任意一个字符
[0-9]  匹配数字0~9中的任意一个字符

2. Matching position

^ Matches the beginning of a string

$ Matches the end of a string

Matches a word boundary

3. Qualifier

• Match the previous character zero or more times
• Match the previous character one or more times

? Match the previous character zero or one time

{n,m} Match the previous character at least n times and at most m times

{n,} Match the previous character at least n times

{n} Match only the previous character Characters n times

4. Special characters

. Matches any character except newline characters

Escape characters, you can escape the following characters For special characters

| Or, it can match any successful result of multiple patterns

() Grouping, multiple patterns can be combined to form a more complex pattern

3. Chinese and English mixed string matching practice

Next, we will use examples to demonstrate how to use Python regular expressions to match Chinese and English mixed strings.

1. Match English characters

First, we need to match pure English characters. In regular expressions, a-zA-Z means matching all uppercase and lowercase letters, so we only need to use [a-zA-Z] to match one or more English characters.

For example, if we want to match English characters in the string "Hello World", we can use the following code:

import re

str = "Hello World"
pattern = '[a-zA-Z]+'
result = re.findall(pattern, str)

print(result)

The output result is: ["Hello", "World"], successful match two English words.

2. Match Chinese characters

Next, let’s match Chinese characters. Since the range of Chinese characters is relatively wide, we can use the unicode encoding range to match Chinese characters. The unicode encoding range of Chinese is u4e00-u9fa5, so we can use [u4e00-u9fa5] to match one or more Chinese characters.

For example, if we want to match Chinese characters in the string "Hello World", we can use the following code:

import re

str = "你好世界"
pattern = '[u4e00-u9fa5]+'
result = re.findall(pattern, str)

print(result)

The output result is: ["Hello", "World"], Two Chinese words were successfully matched.

3. Match Chinese and English characters

Finally, let’s match a mixed string of Chinese and English characters. When matching Chinese and English strings, you need to consider both Chinese and English characters. Therefore, we can combine the patterns of Chinese characters and English characters to form the following regular expression:

pattern = '[a-zA-Z]+|[u4e00-u9fa5]+'

This regular expression uses the | symbol to connect the two patterns, which can match one or more English words or Chinese words.

For example, if we want to match Chinese and English words in the string "Hello Hello World World", we can use the following code:

import re

str = "Hello 你好 World 世界"
pattern = '[a-zA-Z]+|[u4e00-u9fa5]+'
result = re.findall(pattern, str)

print(result)

The output result is: ["Hello", "Hello ", "World", "世界"], successfully matched four Chinese and English words.

Summary:

The above is how to use Python regular expressions to match Chinese and English mixed strings. With the above method, we can easily solve the problem of mixed Chinese and English string matching and perform more efficient and accurate text processing.

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