How to read file line by line using for loop in Python?

How to read file line by line using for loop in Python?

I'd be happy to explain how to read a file line by line using a for loop in Python!

Reading files line by line is a common task in many programming languages, including Python. In this case, we'll use the open() function and the for loop to iterate over each line in the file.

Let's start with an example. Suppose you have a text file named "example.txt" with the following content:

Hello, world!
This is just a test.
It has multiple lines.

To read this file line by line using a for loop, we'll follow these steps:

with open('example.txt', 'r') as file:
Read the file line by line using a for loop
pass

with open('example.txt', 'r') as file:
for line in file:
Process the current line
pass

with open('example.txt', 'r') as file:
for line in file:
print(line.strip())

Here's our final code:

with open('example.txt', 'r') as file:
for line in file:
print(line.strip())

Now, when you run this Python script, it will read the lines from your text file and display each line separately. For example, the output would be:

Hello, world!
This is just a test.
It has multiple lines.

That's it! We've successfully read our text file line by line using a for loop in Python.

How to read file line by line in while loop Python?

Here's a step-by-step guide on how to read a file line by line in Python using a while loop.

Step 1: Open the File

To start, you need to open the file you want to read. You can do this using the built-in open() function in Python. The syntax is open(filename, mode), where filename is the name of your file and mode is the way you want to open it. In this case, we'll use 'r' as our mode, which means we're opening the file for reading.

Here's how to do it:

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

Replace 'example.txt' with your own file name.

Step 2: Read the File Line by Line

Now that we have our file open, let's read it line by line. We'll use a while loop to do this. The idea is that we keep reading lines from the file as long as there are more lines to read. When we've reached the end of the file, the loop will exit.

Here's how to do it:

line = file.readline()
while line:
Do something with each line
print(line.strip())
line = file.readline()

Let's break this down:

Step 3: Close the File

When you're done reading the file, don't forget to close it! This is important because files can be locked by other processes if they remain open. To close a file, simply use the close() method:

file.close()

Here's the complete code:

file = open('example.txt', 'r')
line = file.readline()
while line:
print(line.strip())
line = file.readline()
file.close()

This is how you read a file line by line in Python using a while loop. Remember to replace 'example.txt' with your own file name!

Tips and Variations

I hope this helps! Let me know if you have any questions.