Detailed explanation of Python string search and statistics methods

1. count() method counts the number of occurrences of strings

The count() method is used to count the number of times a substring appears in the original string. This method is very practical, especially when text analysis is required.

Basic syntax

(sub[, start[, end]])

Parameter description:

• sub: substring to search
• start: optional, the location to start search, default is 0
• end: optional, the location where the search ends, default to the end of the string

Example of usage

# Basic usagetext = "Python is a great programming language, Python is simple and easy to learn, and Python is powerful"
count = ("Python")
print(f"'Python'Appears in the text{count}Second-rate")  # Output: 'Python' appears 3 times in the text
# Specify the search rangepartial_count = ("Python", 10, 30)
print(f"Within the specified range'Python'Appeared{partial_count}Second-rate")

# Statistical punctuation markstext = "Hello, World! How are you?"
comma_count = (",")
print(f"逗号Appeared{comma_count}Second-rate")  # Output: The comma appears once

2. The find() method detects the position of the substring

The find() method is used to find the first occurrence of a substring in a string, and returns -1 if it cannot be found. This method is very useful when you need to locate a specific text location.

Basic syntax

(sub[, start[, end]])

Parameter description:

• sub: substring to search
• start: optional, the location to start search, default is 0
• end: optional, the location where the search ends, default to the end of the string

Example of usage

# Basic searchtext = "Python programming is fun"
position = ("programming")
print(f"'programming'The location is：{position}")  # Output: 'Programming' position is: 6
# Find a substring that does not existposition = ("Java")
print(f"'Java'The location is：{position}")  # Output: 'Java' is at:-1
# Specify the search rangetext = "Python is great, Python is powerful"
position = ("Python", 5)
print(f"From location5Start searching'Python'The location is：{position}")

3. Index() method detects the position of the substring

The index() method is very similar to the find() method, and is used to find the position of the substring in the string. The main difference is: when the substring cannot be found, index() will throw a ValueError exception, and find() will return -1.

Basic syntax

(sub[, start[, end]])

Parameter description:

• sub: substring to search
• start: optional, the location to start search, default is 0
• end: optional, the location where the search ends, default to the end of the string

Example of usage

# Basic usetext = "Python programming is fun"
try:
    position = ("programming")
    print(f"'programming'The location is：{position}")  # Output: 'Programming' position is: 6    
    # Find a substring that does not exist    position = ("Java")
except ValueError:
    print("No specified substring found!")

# Specify the search rangetext = "Python is great, Python is powerful"
try:
    position = ("Python", 5)
    print(f"From location5Start searching'Python'The location is：{position}")
except ValueError:
    print("No substring found within the specified range!")

The difference between find() and index() methods

1. Different return values：

   • find(): Return -1 when the substring cannot be found
   • index(): ValueError exception thrown when substring cannot be found

2. Use scenarios：

   • find(): When you are not sure whether the substring exists and need to make a conditional judgment
   • index(): When you are sure that the substring must exist, or you need to catch exceptions for special processing

# find() method exampletext = "Hello, World!"
position = ("Python")
if position != -1:
    print(f"Find the substring，Location is：{position}")
else:
    print("Substring not found")

# index() method exampletry:
    position = ("Python")
    print(f"Find the substring，Location is：{position}")
except ValueError:
    print("Substring not found")

Summarize

This tutorial introduces in detail three commonly used string search and statistics methods in Python:

1. count() method: Used to count the number of times substrings appear
2. find() method: Used to find the substring location, return -1 if not found
3. index() method: Used to find the location of the substring, no exception was found

These methods are often used in text processing, and mastering them can help you better handle string-related programming tasks. Depending on the specific usage scenario, you can choose the most suitable method:

• When counting the number of occurrences, use count()
• When you need to find the location safely, use find()
• When the substring must exist, use index()

This is the end of this article about the detailed explanation of Python string search and statistical methods. For more related Python string search and statistical content, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!