Usage of sub() in Python

sub() in Python is a function in the re module, which is used to perform regular expression replacement operations. You can search for parts that match a certain regular expression pattern in a string and replace it with The basic syntax for the specified content is "re.sub(pattern, repl, string, count=0, flags=0)". It should be noted that the sub() function uses greedy mode for replacement by default, that is, matching as much as possible Longer section.

In Python, sub() is a function in the re module, used to perform regular expression replacement operations. The sub() function can search for parts of a string that match a regular expression pattern and replace it with the specified content. The basic syntax of the

sub() function is as follows:

re.sub(pattern, repl, string, count=0, flags=0)

Among them, the parameter meaning is as follows:

• pattern: the regular expression pattern to be matched.
• repl: String used to replace the matched part.
• string: The original string to be replaced.
• count (optional): Specify the maximum number of replacements. The default is 0, which means replacing all matching parts.
• flags (optional): Flags used to control how regular expressions are matched.

The following is a simple example that demonstrates how to use the sub() function to perform a replacement operation:

import re

text = "Hello, world! This is a test."
new_text = re.sub(r"\bworld\b", "Python", text)
print(new_text)  # 输出：Hello, Python! This is a test.

In the above code, the string is matched by the regular expression \bworld\b The word "world" in the string is then replaced with the string "Python" to obtain a new string "Hello, Python! This is a test."

It should be noted that the sub() function uses greedy mode for replacement by default, that is, matching longer parts as much as possible. If you need non-greedy mode, you can use ? in the regular expression for modification.

In addition, re.sub() also supports using functions as replacement strings, which can dynamically generate replacement results based on the matched content. For detailed usage, please refer to the description of the re module in the official Python documentation.

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