How to use Python regular expressions for interactive programming

With the continuous development of science and technology, the world today has entered the information age, and the development and application of programming languages ​​are becoming more and more widespread. Python, as a high-level programming language known for its simplicity, easy-to-read, and easy-to-learn, is even more popular. In Python, regular expressions are a very important built-in module that must be understood. By using Python regular expressions, you can perform text search, matching, and replacement operations. This article will introduce in detail how to use regular expressions in Python programming.

Part 1: The basis of Python regular expressions

In Python, the first step to use regular expressions is to import the regular expression module, import re.

Next, we can use the functions in the re library, such as search, match, findall, etc., to perform regular expression matching and query. In the following examples, we will take the matching of numbers as an example to introduce the basic usage of regular expressions.

1. match() function

The match() function is one of the most commonly used functions in the re library. It is used to match a regular expression starting from the beginning of the string.

Sample code:

import re 
data = "yue520"
pattern = "yue" 
result = re.match(pattern, data) 
print(result)

In the above code, we use the re.match function to match regular expressions. Among them, pattern is the regular expression pattern, and data is the string to be matched. We can see that in this example, the result output is a matching object. The match object contains the starting position, ending position, matched string and other information of the successfully matched string.

In addition to the match() function, the re library also provides many other functions, such as search(), findall(), sub(), etc. Among them, search() is similar to match(), but the search() function can start matching data from any position.

2. findall() function

The findall() function is used to match regular expressions in the entire string and return all matching results in a list.

Sample code:

import re 
data = "yue520 is handsome yue520"
pattern = "yue" 
result = re.findall(pattern, data) 
print(result)

In this example, we use the findall() function to find all matching "yue" in the data. The output result is a list, that is, ["yue", "yue"], and two yue are matched.

3. sub() function

The sub() function is used to find regular expression patterns in strings and replace the matched strings with the specified strings .

Sample code:

import re 
data = "yue is handsome, yue is awesome"
pattern = "yue"
new_string = "Tom"
result = re.sub(pattern, new_string, data) 
print(result)

In this example, we use the sub() function to replace all matching "yue" in "data" with "Tom". After running, the output result is "Tom is handsome, Tom is awesome".

Part 2: Interactive programming using Python regular expressions

The flexibility and power of regular expressions make it play an extremely important role in daily programming. The interactive programming platform is more convenient and practical. Below, we will introduce how to use Python regular expressions for interactive programming.

1. Use the search() function of the re library for interactive regular expression matching

In interactive programming, we can use variables to store the input string. Use the search() function in the re library to match regular expressions, and then output the matching results.

Sample code:

import re 
while True:
    data = input("请输入待匹配的字符串:") 
    pattern = input("请输入正则表达式模式: ") 
    result = re.search(pattern, data) 
    if result:
        print("匹配成功！匹配结果为：", result.group()) 
    else:
        print("匹配失败！")

In this example, we use the while True loop to achieve the effect of interactive programming. First, call the input() function to read the input string and regular expression pattern, and then use the re.search() function to match the regular expression. If the match is successful, the result is output; if the match fails, "Match failed!" is output.

2. Use the sub() function of the re library to match and replace interactive regular expressions

In interactive programming, you can enter the string to be matched, the regular expression and Replace string information and other information to perform regular expression matching and replacement. In this case, we can quickly solve the problem using the sub() function in the re library.

Sample code:

import re 
while True:
    data = input("请输入待匹配的字符串:") 
    pattern = input("请输入正则表达式模式: ") 
    new_string = input("请输入替换的字符串: ") 
    result = re.sub(pattern, new_string, data) 
    print("替换后的结果为：", result) 

In this example, we also use the while True loop to implement interactive programming. Read the input string, regular expression, replacement string and other information through the input() function, and then use the re.sub() function to perform matching and replacement. Finally, the replacement result is output.

Summary:

Python regular expressions play a huge role in text operations. This article starts with basic knowledge and introduces in detail how to use Python regular expressions for interactive programming through some sample codes. Although using regular expressions in interactive programming is not a very advanced operation, the small tool of regular expressions can indeed bring great convenience to our daily development. Understanding the basic knowledge and simple applications of regular expressions is an essential skill in Python programming.

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