What are the string search and replace techniques in Python?

What are the string search and replacement techniques in Python? (Specific code examples)

In Python, strings are a common data type. We often encounter string search and replace operations in daily programming. This article will introduce some common string search and replacement techniques, accompanied by specific code examples.

1. Find substring

To find a specific substring in a string, you can use the find() method or index of the string ()method.

• find()The method returns the index of the first occurrence of the substring in the string, or -1 if it does not exist.
  The sample code is as follows:

s = "Hello, World!"
index = s.find("World")
print(index)  # 输出：7

• index() method is similar to the find() method, returning the substring in the string The position index of the first occurrence, but if it does not exist, a ValueError exception will be thrown.
  The sample code is as follows:

s = "Hello, World!"
try:
    index = s.index("World")
    print(index)  # 输出：7
except ValueError:
    print("未找到子串")

In addition to the above two methods, we can also use regular expressions to find specific substrings. Python provides the re module to support regular expression operations.

• Using regular expressions to find substrings The sample code is as follows:

import re

s = "Hello, World!"
pattern = r"l+"
matches = re.findall(pattern, s)
print(matches)  # 输出：['ll', 'l']

2. Replace substring

Replace in string Specific substrings can be specified using the string's replace() method.

• replace() method can replace a certain substring in a string with another specified string.
  The sample code is as follows:

s = "Hello, World!"
new_s = s.replace("World", "Python")
print(new_s)  # 输出：Hello, Python!

• Of course, we can also use regular expressions for replacement.
  The sample code is as follows:

import re

s = "Hello, World!"
pattern = r"l+"
new_s = re.sub(pattern, "123", s)
print(new_s)  # 输出：He123o, Wor123d!

In addition to the above methods, we can also use string slicing and splicing to implement replacement operations. This method is suitable for replacing only part of the string.

• The sample code for using string slicing and splicing is as follows:

s = "Hello, World!"
new_s = s[:5] + "Python" + s[11:]
print(new_s)  # 输出：Hello, Python!

Summary:

This article introduces string search and replacement techniques in Python, And specific code examples are given. Whether you use the built-in methods of strings or use regular expressions, you can achieve string search and replace operations. In actual programming, we can choose the appropriate method to implement string operations according to the specific situation.

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