Introduction
Almost every program needs to work with files — whether it’s
saving user data, reading configuration settings, or processing text. Python
makes file handling simple and powerful. In this tutorial, we’ll explore how to
open, read, write, and close files, along with best practices for safe
file management.
Step 1: Opening a File
Python uses the built-in open()
function to work with files.
Code:
file = open("example.txt", "r")
- "example.txt" is the file name.
- "r" means read mode.
Common modes:
- "r"
→ Read (default)
- "w"
→ Write (creates/overwrites file)
- "a"
→ Append (adds to file)
- "b"
→ Binary mode (e.g., images, PDFs)
Step 2: Reading Files
You can read the entire file or line by line.
Code:
file = open("example.txt", "r")
content = file.read()
print(content)
print(len(content))
file.close()
Always close the file after use with file.close().
Reading line by line:
Code:
file = open("example.txt", "r")
for line in file:
print(line.strip())
print(len(line.strip()))
file.close()
Step 3: Writing to Files
Use "w" mode to
write (overwrites existing content).
Code:
file = open("example.txt", "w")
file.write("Hello, Python!\n")
file.write("This is a new line.")
file.close()
If the file doesn’t exist, Python creates it.
Code:
file = open("example.txt", "a")
file.write("\nAdding another line.")
file.close()
Step 4: Using with Statement (Best Practice)
Instead of manually closing files, use with. It
automatically handles closing.
Code:
with open("example.txt", "r") as file:
content =
file.read()
print(content)
This is the recommended way to handle files safely.
Step 5: Reading and Writing Together
You can combine reading and writing:
Code:
with open("example.txt", "r+") as file:
content =
file.read()
file.write("\nNew content
added.")
- "r+"
allows both reading and writing.
- File
pointer starts at the beginning.
Step 6: Working with Binary Files
For non-text files (like images), use binary mode:
Code:
with open("eml_image.jpeg", "rb") as file:
data = file.read()
print(len(data)) # Prints size
in bytes
Binary mode is essential for handling files beyond plain
text.
Mini Exercise
Try this challenge:
- Create
a new file called notes.txt.
- Write
three lines of text into it.
- Reopen
the file and read the content.
- Append
one more line and print the final content.
Hint:
Code:
Step 1: Write
with open("notes.txt", "w") as file:
file.write("Line 1\nLine 2\nLine 3\n")
Step 2: Read
with open("notes.txt", "r") as file:
print(file.read())
Step 3: Append
with open("notes.txt", "a") as file:
file.write("Line 4\n")
Step 4: Final Read
with open("notes.txt", "r") as file:
print(file.read())
Conclusion
In this tutorial, you learned how to:
- Open
files in different modes (r, w, a, b)
- Read
and write text files
- Use
the with statement for safe handling
- Work
with binary files
File handling is a core skill for real-world applications.
With it, you can build programs that store data, process logs, or manage
documents.
In the next tutorial, we’ll explore error handling and
exceptions — how to make your programs robust and prevent crashes.