Memory-mapped files in Operating Systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a memory-mapped file in Python.

Operating Systems

import mmap
with open('example.txt', 'r+b') as f:
    mm = mmap.mmap(f.fileno(), [1])
    print(mm.readline())

Drag options to blanks, or click blank then click option'

A1024

B-1

C0

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 or -1 as size causes errors or unexpected behavior.

The size parameter in mmap.mmap specifies the number of bytes to map. Using 1024 maps 1 KB of the file.

2fill in blank

medium

Complete the code to open a memory-mapped file with read-only access.

Operating Systems

import mmap
with open('data.bin', 'rb') as f:
    mm = mmap.mmap(f.fileno(), 0, access=[1])
    print(mm.read(10))

Drag options to blanks, or click blank then click option'

Ammap.ACCESS_WRITE

Bmmap.ACCESS_DEFAULT

Cmmap.ACCESS_COPY

Dmmap.ACCESS_READ

Attempts:

3 left

💡 Hint

Common Mistakes

Using ACCESS_WRITE allows writing, which is not desired here.

Using mmap.ACCESS_READ opens the memory map with read-only access, preventing modifications.

3fill in blank

hard

Fix the error in the code to correctly map the entire file size.

Operating Systems

import os
import mmap
filename = 'logfile.log'
size = os.path.getsize(filename)
with open(filename, 'r+b') as f:
    mm = mmap.mmap(f.fileno(), [1])
    print(mm[:10])

Drag options to blanks, or click blank then click option'

A-1

B0

Csize

Dlen(filename)

Attempts:

3 left

💡 Hint

Common Mistakes

Passing 0 maps the whole file only on some systems, which is not portable.

The size variable holds the file size, which should be passed to mmap to map the entire file.

4fill in blank

hard

Fill both blanks to create a memory-mapped file and write data to it.

Operating Systems

import mmap
with open('file.dat', 'r+b') as f:
    mm = mmap.mmap(f.fileno(), [1], access=[2])
    mm[0:5] = b'Hello'
    mm.flush()

Drag options to blanks, or click blank then click option'

A10

Bmmap.ACCESS_READ

Cmmap.ACCESS_WRITE

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using ACCESS_READ prevents writing and causes errors.

Mapping 10 bytes with ACCESS_WRITE allows writing data and flushing changes to the file.

5fill in blank

hard

Fill all three blanks to create a memory-mapped file, read a slice, and close it properly.

Operating Systems

import mmap
with open('sample.txt', 'r+b') as f:
    mm = mmap.mmap(f.fileno(), [1], access=[2])
    data = mm[[3]:[3]+5]
    print(data)
    mm.close()

Drag options to blanks, or click blank then click option'

A20

Bmmap.ACCESS_READ

C10

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using ACCESS_WRITE when only reading is needed.

Mapping 20 bytes with read access and reading from offset 0 to 5 bytes correctly reads data from the file.