How to read a text file in Python: Syntax and examples

Using the open() function

When working with text files in Python, the first step is to open the file using the open() function. The open() function takes two parameters: the name of the file and the mode in which you want to open the file.

Here is the syntax to open a text file:

file = open("filename.txt", "mode")

The filename.txt is the name of the text file you want to open, and the mode specifies how you want to interact with the file.

Specifying the file mode

When opening a file, you need to specify the mode in which you want to open the file. The mode parameter is a string that consists of one or more characters, each representing a specific mode.

Here are some of the most commonly used file modes:

• «r»: Read mode – opens the file for reading (default mode).
• «w»: Write mode – opens the file for writing. If the file does not exist, it creates a new file. If the file exists, it truncates the file to zero length.
• «a»: Append mode – opens the file for appending. If the file does not exist, it creates a new file.
• «x»: Exclusive creation mode – opens the file for exclusive creation. If the file already exists, the operation fails.

Here is an example of opening a text file in read mode:

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

Reading the entire file

Once you have opened a text file, you can read its contents using various methods. One common method is to read the entire file at once using the read() method.

Here is the syntax to read the entire file:

content = file.read()

The read() method reads the entire contents of the file and returns it as a string. You can then manipulate the content as needed.

Here is an example of reading the entire file:

file = open("filename.txt", "r")
content = file.read()
print(content)
file.close()

Reading line by line

Another common method to read a text file is to read it line by line using the readline() method. This method reads a single line from the file and returns it as a string.

Here is the syntax to read a line from the file:

line = file.readline()

The readline() method reads a single line from the file each time it is called. You can use a loop to read all the lines in the file.

Here is an example of reading a text file line by line:

file = open("filename.txt", "r")
line = file.readline()
while line:
    print(line)
    line = file.readline()
file.close()

Using the with statement

Python provides a more convenient way to work with files using the with statement. The with statement ensures that the file is properly closed after it is used, even if an exception occurs.

Here is the syntax to open a file using the with statement:

with open("filename.txt", "mode") as file:
    # Perform operations on the file

Inside the with block, you can perform any operations on the file, such as reading or writing. Once the block is exited, the file is automatically closed.

Here is an example of using the with statement to read a text file:

with open("filename.txt", "r") as file:
    content = file.read()
    print(content)

Handling exceptions

When working with files, it is important to handle exceptions that may occur. For example, if the file does not exist or if there are permission issues, an exception will be raised.

You can use a try-except block to handle exceptions when working with files. This allows you to gracefully handle any errors that may occur.

Here is an example of handling exceptions when reading a text file:

try:
    file = open("filename.txt", "r")
    content = file.read()
    print(content)
except FileNotFoundError:
    print("File not found.")
except PermissionError:
    print("Permission denied.")
finally:
    file.close()

In this example, the try block attempts to open the file and read its contents. If a FileNotFoundError or PermissionError occurs, the corresponding except block is executed. The finally block ensures that the file is closed, regardless of whether an exception occurred or not.

Closing the file

After you have finished working with a file, it is important to close it using the close() method. Closing the file releases any system resources associated with it and ensures that any changes made to the file are saved.

Here is the syntax to close a file:

file.close()

It is good practice to always close the file after you are done with it to avoid any potential issues.

Here is an example of closing a file:

file = open("filename.txt", "r")
content = file.read()
print(content)
file.close()

By closing the file, you ensure that any changes made to the file are saved and that system resources are freed up.