← Python

File Operations – Open

open() opens a file and returns a file object; the with statement closes it automatically when done

What it does: The with statement automatically closes the file when the block ends. 'a' mode opens the file and adds to the end without erasing existing content. open() connects your program to a file on disk — you then read or write through that connection. 'r' requires the file to exist — only 'w' and 'a' create files automatically. Unclosed files may not flush writes to disk and waste OS file handles. Opening a non-existent file in 'r' mode raises FileNotFoundError. Use try/except. 'w' mode creates or overwrites the file. f.write() writes the string. open() returns a file object. type() shows its class name.

Common mistakes: Missing colon after the with statement. open is lowercase: Open is not valid.

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Learning

Duo

What does open() do?

Opens a file for reading or writingOpens a website

Matches

❌ f = open('data.txt') print(f.read()) f.write('hi')

↓

Error: Can't write in read mode

Applying

Meanings

Term

open()

Meaning

Built-in function that opens a file.

Practice

with open('hello.txt', 'w') as f:

Testing

Gaps

with ('file.txt', 'r') as f:

Check Answer

Spots

1with open('file.txt') as f

2 content = f.read()

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Quick Questions

1. What does open() do?

A. Opens a file for reading or writing ✓

B. Opens a website

open() connects your program to a file on disk — you then read or write through that connection

2. What does 'r' mode mean?

A. Run

B. Read only ✓

'r' is the default mode — it opens the file for reading and fails if file doesn't exist

3. What does 'w' mode do?

A. Writes overwrites existing content ✓

B. Reads the file

'w' creates the file if needed and wipes any existing content before writing

4. What does 'a' mode do?

A. Reads all

B. Appends adds to the end ✓

'a' keeps existing content and adds new content after it — safe for logs

5. Why use 'with open()'?

A. Automatically closes the file ✓

B. It's faster

with ensures the file closes even if an error occurs — no manual .close() needed

Match the Pairs

f = open('data.txt') print(f.read()) f.write('hi') → Error: Can't write in read mode

open('missing.txt', 'r') → Error: FileNotFoundError

with open('f.txt', 'r') as f: data = f.read() → Valid: with auto-closes file

open('f.txt', 'a') → Ok: Append mode — adds to end

with open('f.txt','w') as f: f.write('Hi') → Output: (writes 'Hi' to file)

f = open('f.txt','r') print(type(f)) → Output: <class '_io.TextIOWrapper'>

Key Term

open()

Built-in function that opens a file.~~'r' mode

Fill in the Blanks

1. with open('file.txt', 'r') as f:

2. with open('file.txt', 'r') as f:

3. with open('file.txt', 'w') as f:

4. with open('log.txt', 'a') as f: f.write('entry')

5. f = open('test.txt', 'w') f.write('Hi') f.close()

Spot the Error

Question 1

A with open('file.txt') as f

B content = f.read()

C print(content)

D print('Done')

Line A — Missing colon after the with statement

Question 2

A with Open('file.txt') as f:

B content = f.read()

C print(content)

D print('Done')

Line A — open is lowercase: Open is not valid

Question 3

A # Open without with block

B f = open('file.txt', 'r')

C content = f.read()

D # forgot to close

Line B — File is never closed: always close or use 'with'

Question 4

A with open('file.txt', 'r') as f:

B f.write('Hello')

C print('Written')

D print('Done')

Line B — Can't write in 'r' mode: use 'w' or 'a'

Question 5

A with open(file.txt, 'r') as f:

B content = f.read()

C print(content)

D print('Done')

Line A — Filename must be a string in quotes: 'file.txt'

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