python

Random bytes with os.urandom()

by
Python Practice › OS Module Programs › Program 27

Random bytes with os.urandom()

EasyOS Module Programs · 27 of 49

Write a Python program to get random bytes with os.urandom() and turn them into a string.

Output
bytes 8
16

Approach

  1. os.urandom(n) returns n cryptographically strong random bytes.

Solution

Python
import os data = os.urandom(8)print(type(data).__name__, len(data))print(len(data.hex()))
Output
bytes 8
16

Line by line

Line 3

The bytes differ on every run; hex() turns 8 bytes into 16 hexadecimal characters.

Learn the concept

New to this topic? Read the lesson, then come back.

More os module programs

#28EasyCheck read permission#29EasyFile size with os.path.getsize()#30EasyChange the working directory#31EasyList files with os.scandir()

← All 49 OS Module Programs

Read command-line arguments

by
Python Practice › OS Module Programs › Program 24

Read command-line arguments

EasyOS Module Programs · 24 of 49

Write a Python program that reads arguments passed on the command line.

Output
arguments: ['chrome', '--headless']

Approach

  1. Start a child Python with arguments and read them from sys.argv.

Solution

Python
import subprocessimport sys with open("args_demo.py", "w") as f:    f.write("import sys\nprint('arguments:', sys.argv[1:])\n")out = subprocess.run([sys.executable, "args_demo.py", "chrome", "--headless"], capture_output=True, text=True)print(out.stdout.strip())
Output
arguments: ['chrome', '--headless']

Line by line

Lines 4-5

Writes a tiny script that prints its arguments.

Line 6

Runs it the way you would type python args_demo.py chrome --headless.

Learn the concept

New to this topic? Read the lesson, then come back.

More os module programs

#25EasySystem and Python version#26EasyFolders searched for programs#27EasyRandom bytes with os.urandom()#28EasyCheck read permission

← All 49 OS Module Programs

Backup sorted by extension

by
Python Practice › OS Module Programs › Program 22

Backup sorted by extension

MediumOS Module Programs · 22 of 49

Write a Python backup program that copies every file into a folder named after its extension.

Output
csv ['d.csv']
py ['a.py', 'b.py']
txt ['c.txt']

Approach

  1. Walk the source, compute the extension and copy into backup/<ext>/.

Solution

Python
import osimport shutil os.makedirs("project/docs", exist_ok=True)for path in ["project/a.py", "project/b.py", "project/docs/c.txt", "project/d.csv"]:    with open(path, "w") as f:        f.write("x") for folder, _, files in os.walk("project"):    for name in files:        ext = os.path.splitext(name)[1].lstrip(".") or "no_ext"        target = os.path.join("backup", ext)        os.makedirs(target, exist_ok=True)        shutil.copy2(os.path.join(folder, name), target) for ext in sorted(os.listdir("backup")):    print(ext, sorted(os.listdir(os.path.join("backup", ext))))
Output
csv ['d.csv']
py ['a.py', 'b.py']
txt ['c.txt']

Line by line

Lines 9-14

Every file found by os.walk is copied into a folder for its extension; files without one go to “no_ext”.

Learn the concept

New to this topic? Read the lesson, then come back.

More os module programs

#23EasyRun a system command#24EasyRead command-line arguments#25EasySystem and Python version#26EasyFolders searched for programs

← All 49 OS Module Programs

Run a system command

by
Python Practice › OS Module Programs › Program 23

Run a system command

EasyOS Module Programs · 23 of 49

Write a Python program to run an operating system command and read its output.

Output
return code: 0
Python 3.15.1
hello from the shell

Approach

  1. subprocess.run with capture_output=True is the modern way.

Solution

Python
import subprocessimport sys result = subprocess.run([sys.executable, "--version"], capture_output=True, text=True)print("return code:", result.returncode)print(result.stdout.strip()) echo = subprocess.run("echo hello from the shell", shell=True, capture_output=True, text=True)print(echo.stdout.strip())
Output
return code: 0
Python 3.15.1
hello from the shell

Line by line

Line 4

Passing a list runs the program directly, without a shell, which is safer.

Line 8

shell=True lets you use shell commands such as echo or dir; never combine it with untrusted input.

Learn the concept

New to this topic? Read the lesson, then come back.

More os module programs

#24EasyRead command-line arguments#25EasySystem and Python version#26EasyFolders searched for programs#27EasyRandom bytes with os.urandom()

← All 49 OS Module Programs

Remove files of one extension

by
Python Practice › OS Module Programs › Program 21

Remove files of one extension

EasyOS Module Programs · 21 of 49

Write a Python program to remove all files with a specific extension from a folder.

Output
['keep.txt']

Approach

  1. Loop over the folder and remove matching files.

Solution

Python
import os os.makedirs("logs", exist_ok=True)for name in ["a.log", "b.log", "keep.txt"]:    open(os.path.join("logs", name), "w").close()for name in os.listdir("logs"):    if name.endswith(".log"):        os.remove(os.path.join("logs", name))print(os.listdir("logs"))
Output
['keep.txt']

Learn the concept

New to this topic? Read the lesson, then come back.

More os module programs

#22MediumBackup sorted by extension#23EasyRun a system command#24EasyRead command-line arguments#25EasySystem and Python version

← All 49 OS Module Programs

Remove a file

by
Python Practice › OS Module Programs › Program 20

Remove a file

EasyOS Module Programs · 20 of 49

Write a Python program to remove a file at a given path.

Output
False

Approach

  1. os.remove(); check that it exists first.

Solution

Python
import os open("old.log", "w").close()if os.path.exists("old.log"):    os.remove("old.log")print(os.path.exists("old.log"))
Output
False

Learn the concept

New to this topic? Read the lesson, then come back.

More os module programs

#21EasyRemove files of one extension#22MediumBackup sorted by extension#23EasyRun a system command#24EasyRead command-line arguments

← All 49 OS Module Programs

Copy files of one extension

by
Python Practice › OS Module Programs › Program 18

Copy files of one extension

EasyOS Module Programs · 18 of 49

Write a Python program to copy only the files with a specific extension.

Output
['a.csv', 'c.csv']

Approach

  1. Filter names with endswith, then copy.

Solution

Python
import osimport shutil os.makedirs("src", exist_ok=True)os.makedirs("only_csv", exist_ok=True)for name in ["a.csv", "b.txt", "c.csv"]:    open(os.path.join("src", name), "w").close()for name in os.listdir("src"):    if name.endswith(".csv"):        shutil.copy(os.path.join("src", name), "only_csv")print(sorted(os.listdir("only_csv")))
Output
['a.csv', 'c.csv']

Learn the concept

New to this topic? Read the lesson, then come back.

More os module programs

#19MediumCopy a file into 10 nested folders#20EasyRemove a file#21EasyRemove files of one extension#22MediumBackup sorted by extension

← All 49 OS Module Programs

Copy a file into 10 nested folders

by
Python Practice › OS Module Programs › Program 19

Copy a file into 10 nested folders

MediumOS Module Programs · 19 of 49

Write a Python program to copy a file into 10 different nested directories.

Output
10 ['file1.txt', 'file2.txt']

Approach

  1. Build deeper paths in a loop and copy the file into each.

Solution

Python
import osimport shutil with open("seed.txt", "w") as f:    f.write("sample")path = "tree"for i in range(1, 11):    path = os.path.join(path, f"d{i}")    os.makedirs(path, exist_ok=True)    shutil.copy("seed.txt", os.path.join(path, f"file{i}.txt")) copies = [f for _, _, files in os.walk("tree") for f in files]print(len(copies), copies[:2])
Output
10 ['file1.txt', 'file2.txt']

Line by line

Lines 6-9

Each pass goes one folder deeper and copies the file there.

Line 11

os.walk visits every folder, so all 10 copies are found.

Learn the concept

New to this topic? Read the lesson, then come back.

More os module programs

#20EasyRemove a file#21EasyRemove files of one extension#22MediumBackup sorted by extension#23EasyRun a system command

← All 49 OS Module Programs

Copy a file

by
Python Practice › OS Module Programs › Program 17

Copy a file

EasyOS Module Programs · 17 of 49

Write a Python program to copy a file from a source path to a target path.

Output
quarterly report

Approach

  1. shutil.copy copies data and permissions; copy2 also copies timestamps.

Solution

Python
import osimport shutil os.makedirs("src", exist_ok=True)os.makedirs("dst", exist_ok=True)with open("src/report.txt", "w") as f:    f.write("quarterly report")shutil.copy2("src/report.txt", "dst/report.txt")print(open("dst/report.txt").read())
Output
quarterly report

Learn the concept

New to this topic? Read the lesson, then come back.

More os module programs

#18EasyCopy files of one extension#19MediumCopy a file into 10 nested folders#20EasyRemove a file#21EasyRemove files of one extension

← All 49 OS Module Programs

Count files per extension

by
Python Practice › OS Module Programs › Program 16

Count files per extension

EasyOS Module Programs · 16 of 49

Write a Python program to count the files of each extension in a target path.

Output
{'.csv': 1, '.py': 3, '.txt': 2}

Approach

  1. os.path.splitext plus Counter.

Solution

Python
import osfrom collections import Counter os.makedirs("target", exist_ok=True)for name in ["a.txt", "b.txt", "c.csv", "d.py", "e.py", "f.py"]:    open(os.path.join("target", name), "w").close()counts = Counter(os.path.splitext(n)[1] for n in os.listdir("target"))print(dict(sorted(counts.items())))
Output
{'.csv': 1, '.py': 3, '.txt': 2}

Learn the concept

New to this topic? Read the lesson, then come back.

More os module programs

#17EasyCopy a file#18EasyCopy files of one extension#19MediumCopy a file into 10 nested folders#20EasyRemove a file

← All 49 OS Module Programs