6.3c File Handling in Python — Edexcel 1CP2

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Why File Handling?

Variables are stored in RAM — they are lost when a program ends. Files allow data to be persisted (saved permanently) to secondary storage. File handling is essential for programs that need to save results, load settings, or process data across multiple runs.

Opening and Closing Files

Use the built-in open() function. Always close files when done (or use with which closes automatically).

Mode	Meaning	Creates file?	Overwrites?
`"r"`	Read (default)	No — file must exist	No
`"w"`	Write	Yes	Yes — wipes content
`"a"`	Append	Yes	No — adds to end
`"r+"`	Read and write	No — file must exist	No

Reading from Files

# Method 1: read() — reads the WHOLE file as one string
with open("data.txt", "r") as f:
    content = f.read()
    print(content)

# Method 2: readline() — reads ONE line at a time
with open("data.txt", "r") as f:
    line = f.readline()
    print(line)

# Method 3: readlines() — reads ALL lines into a LIST
with open("data.txt", "r") as f:
    lines = f.readlines()    # ['line1\n', 'line2\n', ...]
    for line in lines:
        print(line.strip())   # .strip() removes \n

# Method 4: iterate directly (most Pythonic)
with open("data.txt", "r") as f:
    for line in f:
        print(line.strip())

Writing to Files

# Write mode — OVERWRITES existing content
with open("output.txt", "w") as f:
    f.write("Hello, World!\n")   # \n adds newline
    f.write("Second line\n")

# Append mode — ADDS to existing content
with open("output.txt", "a") as f:
    f.write("Third line added later\n")

The with Statement

Using with open() as f: is recommended because it automatically closes the file when the block ends — even if an error occurs. This prevents data loss and resource leaks.

# WITHOUT with (manual close — risky)
f = open("file.txt", "r")
content = f.read()
f.close()   # must call this manually

# WITH with (automatic close — recommended)
with open("file.txt", "r") as f:
    content = f.read()
# file is automatically closed here

Exam tip: Edexcel Paper 2 may ask you to write programs that read from or write to text files. Know all three read methods (read, readline, readlines), know that "w" overwrites but "a" appends, and always use the with statement for file handling.

⚠️ Common Mistakes

Using "w" mode when you want to add to a file — "w" wipes ALL existing content!
Forgetting to add "\n" at the end of each line when writing
Not stripping "\n" from lines when reading — each line includes a newline character
Trying to open a file in "r" mode when it doesn't exist — causes FileNotFoundError
Forgetting to close the file when not using 'with' — causes data to not be saved

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Worksheet — 6.3c File Handling

8 Edexcel-style questions · instantly marked

Q1State the difference between opening a file in "w" mode and "a" mode.[2]

✅ Mark scheme

"w" (write) mode overwrites all existing content in the file (or creates it if it doesn't exist) [1]; "a" (append) mode adds new content to the END of the file without removing existing data [1].

Q2Write Python code to write the text "Hello, World!" followed by "Goodbye!" on separate lines to a file called "greetings.txt".[3]

✅ Mark scheme

with open("greetings.txt", "w") as f: [1]; f.write("Hello, World!\n") [1]; f.write("Goodbye!\n") [1]. Must include "\n" for separate lines. Accept print() to file using file=f parameter.

Q3Write Python code to read ALL lines from a file called "names.txt" into a list, then print each name without the newline character.[4]

✅ Mark scheme

with open("names.txt", "r") as f: [1]; lines = f.readlines() [1]; for line in lines: [1]; print(line.strip()) [1]. .strip() removes the newline character (\n) from each line. Accept .rstrip() or .rstrip('\n') instead of .strip().

Q4Why is it recommended to use the 'with' statement when opening files?[2]

✅ Mark scheme

The 'with' statement automatically closes the file when the block ends [1]; this happens even if an error occurs during processing, preventing data loss and resource leaks — no need to call f.close() manually [1].

Q5What is the difference between .read(), .readline(), and .readlines()?[3]

✅ Mark scheme

.read() reads the ENTIRE file content as a single string [1]; .readline() reads ONE line at a time (calling it again gets the next line) [1]; .readlines() reads ALL lines and returns them as a list (each item is a line including \n) [1].

Q6A student opens a file in "r" mode but the file doesn't exist. What happens, and how could this be prevented?[2]

✅ Mark scheme

A FileNotFoundError is raised and the program crashes [1]; prevention: use try/except to handle the error gracefully, or check if the file exists first using os.path.exists() before opening [1].

Q7Write Python code that reads scores from "scores.txt" (one number per line) and calculates the average score.[5]

✅ Mark scheme

with open("scores.txt", "r") as f: [1]; lines = f.readlines() [1]; total = 0; count = 0 [1]; for line in lines: total += int(line.strip()) [1]; count += 1; print(total / count) [1]. Must convert to int/float since file returns strings.

Q8Explain why data stored in a variable is lost when a program ends, but data written to a file is not.[2]

✅ Mark scheme

Variables are stored in RAM (primary storage) which is volatile — it loses its contents when the power is removed or the program ends [1]; files are stored on secondary storage (hard drive / SSD) which is non-volatile — data persists even without power [1].

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Why File Handling?

Opening and Closing Files

Reading from Files

Writing to Files

The with Statement

Worksheet — 6.3c File Handling

Mini Test — File Handling