How To Read Files In Python

Reading files is an essential part of programming, as we often need to process the data stored in a file. In this tutorial, we will learn the various methods of reading files in Python, including using the open() function and some helpful built-in modules.

Step 1: Open a File

To read a file in Python, you first need to open it. You can do this using the built-in open() function. The open() function accepts two arguments: the name of the file and the mode in which the file should be opened.

In this tutorial, we will read a text file called “example.txt” with the following content:
This is an example text file.
It has a couple of lines of text.
To read this file, you can use the following code:

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file = open("example.txt", "r")

Here, "example.txt" is the name of the file, and "r" is the mode in which the file should be opened. There are several modes available, but to read a file, we need to use the “r” (read) mode.

After opening a file, you should close it using the close() method as shown below:

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file.close()

It is a good practice to close the file after using it, to prevent any potential issues or resource leaks.

However, a better alternative to ensure the file is properly closed even in case of exceptions is using the with statement, as shown below:

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with open("example.txt", "r") as file:
    # read the file here
    pass

Using the with statement, the file will be automatically closed when the block of code under it is done executing.

Step 2: Read the Entire File Content

To read the entire content of a file, you can use the read() method, like this:

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with open("example.txt", "r") as file:
    content = file.read()
    print(content)
 
This is an example text file.
It has a couple of lines of text.

Step 3: Read a Single Line of the File

If you want to read a single line of the file, you can use the readline() method. The following code reads the first line of the file:

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with open("example.txt", "r") as file:
    line = file.readline()
    print(line)
 
This is an example text file.

Step 4: Read All Lines as a List

Alternatively, you can read all the lines of the file as a list using the readlines() method:

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with open("example.txt", "r") as file:
    lines = file.readlines()
    print(lines)
 
['This is an example text file.\n', 'It has a couple of lines of text.\n']

Now that you have the file content as a list, you can process it further as needed.

Step 5: Iterate Over the Lines of a File

Instead of reading all the lines at once, you can also iterate over the lines of a file using a for loop:

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with open("example.txt", "r") as file:
    for line in file:
        print(line.strip())  # strip() is used to remove the newline character at the end of the line
 
This is an example text file.
It has a couple of lines of text.

Full Code

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with open("example.txt", "r") as file:
    content = file.read()
    print(content)
 
with open("example.txt", "r") as file:
    line = file.readline()
    print(line)
 
with open("example.txt", "r") as file:
    lines = file.readlines()
    print(lines)
 
with open("example.txt", "r") as file:
    for line in file:
        print(line.strip())

Conclusion

In this tutorial, we have learned different methods to read files in Python, including opening and closing files, reading their content entirely, reading a single line, and iterating over their lines. These methods should provide you with a solid foundation for working with files in Python.