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How to extract specific lines from a text file in Python

How to extract specific lines from a text file in Python.

Here's a step-by-step tutorial on how to extract specific lines from a text file in Python.

Step 1: Open the text file​

To begin, you need to open the text file using the open() function. Specify the file path and mode (read mode 'r' in this case) as arguments. Assign the returned file object to a variable.

file_path = 'path/to/your/file.txt'
file = open(file_path, 'r')

Step 2: Read the file content​

Next, you need to read the contents of the file. You can use the readlines() method to read all the lines from the file and store them as a list.

lines = file.readlines()

Step 3: Extract specific lines​

Now that you have all the lines stored in the lines variable, you can extract specific lines based on your requirements. Here are a few examples:

Example 1: Extract a single line by index​

To extract a single line at a specific index, you can use indexing on the lines list. Remember that indexing starts at 0.

line_index = 3  # Index of the line you want to extract
specific_line = lines[line_index]
print(specific_line)

Example 2: Extract multiple lines within a range​

If you want to extract multiple lines within a specific range, you can use slicing on the lines list. Specify the start and end indexes (exclusive) to extract lines between them.

start_index = 2  # Start index of the range
end_index = 5  # End index of the range
specific_lines = lines[start_index:end_index]
for line in specific_lines:
    print(line)

Example 3: Extract lines based on a condition​

In some cases, you may want to extract lines that meet certain conditions. For instance, lines containing a specific keyword. You can iterate over the lines list and check each line using an if statement.

keyword = 'example'  # Keyword to search for
for line in lines:
    if keyword in line:
        print(line)

Step 4: Close the file​

After you have finished working with the file, it's important to close it using the close() method to free up system resources.

file.close()

That's it! You now have a step-by-step guide on extracting specific lines from a text file in Python. Remember to replace 'path/to/your/file.txt' with the actual path to your text file.