Handling Files

Sometimes you want your program to remember data even after it closes — like a list of scores or entries a user has added. That’s where files come in. Python makes it easy to read data from a file and write data to one.

Opening a file

Use the open() function to open a file. You pass it the filename and a mode that tells Python what you want to do with it:

my_file = open("scores.txt", "r")

This opens scores.txt in read mode and stores the result in a variable. You’ll use that variable to read or write.

Reading from a file

The most common way to read is to loop over the file line by line:

my_file = open("scores.txt", "r")
for line in my_file:
    print(line.strip())
my_file.close()

Each pass through the loop gives you the next line as a string. .strip() removes the newline character at the end — you’ll almost always want that.

If you need the whole file at once as a single string, use read():

my_file = open("scores.txt", "r")
content = my_file.read()
print(content)
my_file.close()

If you want all the lines as a list, use readlines():

my_file = open("scores.txt", "r")
lines = my_file.readlines()  # returns ["line 1\n", "line 2\n", ...]
my_file.close()

For most projects, the for line in file loop is all you need.

Writing to a file

Open in write mode and use the write() method:

my_file = open("scores.txt", "w")
my_file.write("Alice: 95\n")
my_file.write("Bob: 88\n")
my_file.close()

my_file = open("scores.txt", "a")
my_file.write("Carol: 92\n")
my_file.close()

Closing a file

Always close the file when you’re done with close(). This saves everything to disk and frees up resources — think of it like saving and closing a document.

my_file.close()

Using with (recommended)

A cleaner way to work with files is the with block. It closes the file automatically when the block ends, even if something goes wrong:

with open("scores.txt", "r") as my_file:
    for line in my_file:
        print(line.strip())

You don’t need to call close() yourself. Once the indented block finishes, Python handles it. This is the pattern you’ll see most often in real code.