Python File Write, Create, and Delete

Before we begin, let us quickly recap a few ideas from earlier lessons that this lesson builds on.

Quick Recap: What is a File?

A file is like a notebook stored on your computer. It has a name, a location (path), and content. Python can open these notebooks, read from them, write into them, and even throw them away.

Quick Recap: The open() Function and with Statement

In Lesson 22, you learned that open() is Python's way of gaining access to a file:

with open("myfile.txt", "r") as f:
    content = f.read()
    print(content)

• "myfile.txt" · the name (and path) of the file.
• "r" · the mode: "r" means open for reading.
• with · ensures the file is automatically closed when Python is done.
• f · the variable that represents the open file object.
• f.read() · reads all the content of the file as one string.

In this lesson, we will use different mode letters · "a", "w", and "x" · to write to and create files instead of just reading them.

Quick Recap: The os Module

Python's os module is a built-in toolkit for working with your operating system · things like files, folders, and paths. You do not need to install it. You just import it at the top of your script:

import os

We will use it later in this lesson to delete files and folders.

1.1 · What Does "Writing to a File" Mean?

Writing to a file means putting text (or data) into a file from your Python program.

Think of it like this: you have a notebook (the file). Writing to it means picking up a pen and actually putting words on the page. There are two very different ways you can do this:

• Overwriting · you flip to page 1, erase everything, and start writing fresh. Whatever was there before is gone.
• Appending · you flip to the last page and continue writing from where the content left off. The old content stays untouched.

Python gives you both options through different mode letters inside open().

1.2 · File Opening Modes for Writing

When you call open("filename.txt", mode), the second argument (the mode) tells Python what you want to do with the file:

Remember: If you use "r" but the file doesn't exist, Python raises a FileNotFoundError. But "a", "w", and "x" can all create a file if needed.

1.3 · The "a" Mode: Appending Content to a File

What Is Appending?

Appending means adding new content at the end of a file. It does not touch or remove anything that was already there.

Real-life analogy: Imagine a school attendance register. Every day, the teacher adds a new day's record at the bottom of the page. They never erase the old records. That is exactly what "a" mode does.

How Does It Work?

with open("demofile.txt", "a") as f:
    f.write("Now the file has more content!")

Line by line:

• open("demofile.txt", "a") · Open demofile.txt for appending. If the file doesn't exist yet, Python will create it.
• as f · Name the open file f so we can use it inside the with block.
• f.write("Now the file has more content!") · Write (add) this text to the end of the file.
• The with block closes the file automatically when done.

Full Example: Append, Then Read Back

# Step 1: Append new text to the file
with open("demofile.txt", "a") as f:
    f.write("Now the file has more content!")

# Step 2: Open and read the file to confirm
with open("demofile.txt") as f:
    print(f.read())

Expected output in the terminal (assuming the file already contained "Hello, Lagos!"):

Hello, Lagos!Now the file has more content!

Notice: The new text was added right after the last character of the old content, with no automatic space or new line. If you want the new text to appear on a new line, add \n (newline character) at the start of your text:

python❐ Copy

f.write("\nNow the file has more content!")

This would produce:

code❐ Copy

Hello, Lagos!
Now the file has more content!

1.4 · The "w" Mode: Overwriting a File

What Is Overwriting?

Overwriting means erasing everything currently in the file and replacing it with entirely new content. Think of it like using correction fluid on a form · the old text is gone, and you write fresh content on top.

⚠️ Warning: The "w" mode is powerful and dangerous if misused. Everything in the file is permanently deleted the moment you open it in "w" mode · even before you call f.write(). Always double-check before using "w" on an important file.

Simple Overwrite Example

# This will ERASE all existing content in demofile.txt
with open("demofile.txt", "w") as f:
    f.write("Woops! I have deleted the content!")

# Now read back to confirm
with open("demofile.txt") as f:
    print(f.read())

Expected output:

Woops! I have deleted the content!

Everything that was in the file before is gone. Only the new text remains.

1.5 · Append vs. Overwrite: Side-by-Side Comparison

This is an important distinction that confuses many beginners. Study this table carefully:

Quick mental test:

Imagine notes.txt currently contains: Chidi scored 80 in Maths.

After running:

with open("notes.txt", "a") as f:
    f.write(" Amaka scored 95 in English.")

The file now contains:

Chidi scored 80 in Maths. Amaka scored 95 in English.

But after running:

with open("notes.txt", "w") as f:
    f.write("Tunde scored 70 in Science.")

The file now contains only:

Tunde scored 70 in Science.

The earlier content about Chidi and Amaka is gone forever.

Thinking prompt: What would happen if you opened a file with "w" and then never called f.write() at all? The file would become completely empty. This is a common accidental mistake!

2.1 · Why Would You Create a New File?

Sometimes you need to create a file that did not exist before · for example:

• Creating a new log file for a fresh day's records.
• Starting a new configuration file for your application.
• Saving a report generated by your program.

Python provides three modes that can all create a new file:

2.2 · The "x" Mode: Safe File Creation

The "x" mode is the safest way to create a brand new file. It is specifically designed for creation:

• If the file does not exist → Python creates it as an empty file.
• If the file already exists → Python raises a FileExistsError and stops. This protects you from accidentally overwriting an important existing file.

Example

f = open("myfile.txt", "x")

Expected result: A new, empty file called myfile.txt is created in the current working directory.

If you run this exact same line again, Python will raise:

FileExistsError: [Errno 17] File exists: 'myfile.txt'

This is a safety net · it is telling you: "Hey! This file already exists. Are you sure you want to do this?"

2.3 · Creating a File Using "a" Mode

If you open a file with "a" and the file does not exist yet, Python quietly creates it for you without complaining:

with open("newlogfile.txt", "a") as f:
    f.write("System started at 08:00.\n")

Expected result: A file called newlogfile.txt is created with this content:

System started at 08:00.

If the file already existed, this line would simply be added to the end.

2.4 · Creating a File Using "w" Mode

Similarly, "w" mode will create the file if it doesn't exist:

with open("report.txt", "w") as f:
    f.write("Monthly Sales Report\n")
    f.write("Total: ₦4,500,000\n")

Expected result: A file called report.txt is created with this content:

Monthly Sales Report
Total: ₦4,500,000

Key reminder: If report.txt already existed with important data inside it, that data would be completely erased.

2.5 · Writing Multiple Lines to a File

You can call f.write() multiple times, and each call adds text right after the previous one. Use \n (the newline character) to move to a new line:

with open("students.txt", "w") as f:
    f.write("Adaeze - 92\n")
    f.write("Emeka - 87\n")
    f.write("Funmi - 95\n")
    f.write("Babatunde - 88\n")

# Verify by reading back
with open("students.txt") as f:
    print(f.read())

Expected output:

Adaeze - 92
Emeka - 87
Funmi - 95
Babatunde - 88

What is \n? It is the escape character for a new line. When Python writes \n into a file, the next character appears on the line below. It's invisible in the file output but moves the cursor down one row. Think of it as pressing the Enter key on your keyboard.

3.1 · Why Would You Delete a File?

Deleting files is just as important as creating them. In real-world software, you might need to:

• Remove a temporary file after it has been processed.
• Clean up log files that are old and no longer needed.
• Delete a user's data when they close their account.
• Remove test files after testing is complete.

Python handles deletion through the os module · a built-in module that lets Python interact with your computer's operating system.

3.2 · The os Module: A Quick Introduction

What is a module? A module is a file containing Python code that you can import and use in your own scripts. Python comes with many built-in modules. You do not install them · you just import them.

What is the os module? The os module gives Python the ability to interact with the operating system · things like creating folders, deleting files, checking if paths exist, and navigating the file system.

To use it, always write this at the very top of your script:

import os

This one line loads the module into memory and makes all its functions available to you.

3.3 · Deleting a File with os.remove()

What Does os.remove() Do?

os.remove() permanently deletes a file from your computer.

⚠️ Critical Warning: This deletion is permanent. Unlike moving something to the Recycle Bin, os.remove() bypasses it completely. The file is gone immediately. There is no "undo." Always be 100% certain before using this.

Syntax

os.remove("filename.txt")

• os · the module you imported.
• .remove() · the function inside the module that deletes a file.
• "filename.txt" · the name (and path if needed) of the file to delete.

Simple Example

import os

os.remove("demofile.txt")

Expected result: The file demofile.txt is permanently deleted. There is no output printed · it just disappears from your file system.

3.4 · The Problem: What If the File Doesn't Exist?

If you try to delete a file that does not exist, Python raises a FileNotFoundError:

import os

os.remove("ghost_file.txt")  # This file doesn't exist!

Error output:

FileNotFoundError: [Errno 2] No such file or directory: 'ghost_file.txt'

Your entire program would crash at that point. In a real application, this could be catastrophic.

3.5 · The Safe Approach: Check Before You Delete

Python gives you a way to check if a file exists before trying to delete it: os.path.exists().

What Does os.path.exists() Return?

• True · if the file (or folder) at that path exists.
• False · if it does not exist.

Safe Delete Pattern

import os

if os.path.exists("demofile.txt"):
    os.remove("demofile.txt")
else:
    print("The file does not exist")

Line by line:

• import os · loads the os module.
• if os.path.exists("demofile.txt"): · checks whether the file exists. Returns True or False.
• os.remove("demofile.txt") · only runs if the file actually exists (condition was True).
• else: · if the condition was False (file not found).
• print("The file does not exist") · gives a friendly message instead of crashing.

Expected output (if the file exists): No output. The file is silently deleted.

Expected output (if the file does NOT exist):

The file does not exist

This is the pattern you should always use in real projects. Never call os.remove() without first checking that the file exists. It takes two extra lines and can save you from program-breaking crashes.

3.6 · Deleting a Folder with os.rmdir()

What if you want to delete an entire folder instead of just a file?

Use os.rmdir():

import os

os.rmdir("myfolder")

Expected result: The folder named myfolder is permanently deleted.

Very Important Rule: The Folder Must Be Empty

os.rmdir() only works on empty folders. If the folder contains any files or subfolders, Python will raise an OSError:

OSError: [Errno 39] Directory not empty: 'myfolder'

Why this restriction? It is a safety measure. Python does not want you to accidentally delete a folder that has important files inside it. If you want to delete a folder and everything in it, you would need to first delete all files inside it (covered in more advanced lessons using shutil.rmtree()).

Safe Folder Deletion Pattern

Just like with files, you should check before deleting a folder:

import os

if os.path.exists("myfolder"):
    os.rmdir("myfolder")
else:
    print("The folder does not exist")

3.7 · Summary: os.remove() vs os.rmdir()

Mistake 1: Using "w" When You Meant "a"

The error:

# You want to ADD a new entry to your log
with open("daily_log.txt", "w") as f:   # WRONG mode!
    f.write("New entry for today.\n")

What happens: All previous log entries are erased forever. Only the new entry remains.

The fix:

with open("daily_log.txt", "a") as f:   # Correct mode
    f.write("New entry for today.\n")

Rule of thumb: If you want to keep old content, always use "a". Only use "w" when you intentionally want to start fresh.

Mistake 2: Forgetting \n · All Text Runs Together

The error:

with open("names.txt", "w") as f:
    f.write("Chidi")
    f.write("Amaka")
    f.write("Tobi")

Resulting file content:

ChidiAmakaTobi

All names are squashed together on one line with no separating spaces or line breaks.

The fix:

with open("names.txt", "w") as f:
    f.write("Chidi\n")
    f.write("Amaka\n")
    f.write("Tobi\n")

Resulting file content:

Chidi
Amaka
Tobi

Mistake 3: Calling os.remove() Without Checking if the File Exists

The error:

import os
os.remove("report.txt")   # What if the file isn't there?

What happens: If report.txt doesn't exist, Python raises FileNotFoundError and your program crashes.

The fix:

import os
if os.path.exists("report.txt"):
    os.remove("report.txt")
else:
    print("Nothing to delete.")

Mistake 4: Forgetting to Import os Before Using It

The error:

os.remove("myfile.txt")   # Forgot to import os!

What happens: Python raises NameError: name 'os' is not defined.

The fix:

import os   # Always at the top of the script
os.remove("myfile.txt")

Mistake 5: Trying to Delete a Non-Empty Folder with os.rmdir()

The error:

import os
os.rmdir("myproject")   # The folder has files inside it!

What happens: Python raises OSError: [Errno 39] Directory not empty.

The fix (delete files first, then the folder):

import os

# Delete files inside first
os.remove("myproject/notes.txt")
os.remove("myproject/data.csv")

# Now the folder is empty — safe to remove
os.rmdir("myproject")

Mistake 6: Using "x" Mode on a File That Already Exists

The error:

f = open("myfile.txt", "x")   # myfile.txt already exists!

What happens: Python raises FileExistsError: [Errno 17] File exists: 'myfile.txt'.

The fix: Check first, then create:

import os

if not os.path.exists("myfile.txt"):
    f = open("myfile.txt", "x")
    f.close()
    print("File created.")
else:
    print("File already exists — skipping creation.")