MODULE 10: Python Standard Libraries

Python comes with a rich Standard Library that allows developers to perform common tasks without installing external packages.

1. datetime Module

Brief

Used to work with dates and time.

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Common Classes

• date
• time
• datetime
• timedelta

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Get Current Date & Time

from datetime import datetime

now = datetime.now()
print(now)

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Date Formatting

print(now.strftime("%d-%m-%Y %H:%M:%S"))

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Date Arithmetic

from datetime import timedelta

future_date = now + timedelta(days=10)
print(future_date)

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Real-World Use

• Attendance systems
• Logs & timestamps
• Expiry dates

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2. math Module

Brief

Provides mathematical functions.

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Common Functions

import math

print(math.sqrt(16))
print(math.pow(2, 3))
print(math.factorial(5))
print(math.ceil(4.3))
print(math.floor(4.9))

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Constants

print(math.pi)
print(math.e)

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Real-World Use

• Scientific calculations
• Finance & engineering apps

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3. random Module

Brief

Used to generate random numbers.

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Random Integer

import random
print(random.randint(1, 10))

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Random Float

print(random.random())

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Random Choice

colors = ["red", "blue", "green"]
print(random.choice(colors))

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Shuffle List

random.shuffle(colors)
print(colors)

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Real-World Use

• Games
• OTP generation
• Simulations

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4. os & sys Modules

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4.1 os Module

Brief

Used to interact with operating system.

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Common Operations

import os

print(os.getcwd())
os.mkdir("test_folder")
os.rename("test_folder", "demo")
os.remove("file.txt")

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Environment Variables

print(os.environ)

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4.2 sys Module

Brief

Used for system-level operations.

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Examples

import sys

print(sys.version)
print(sys.argv)
sys.exit()

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Real-World Use

• Automation scripts
• CLI tools

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5. shutil Module

Brief

Used for high-level file operations.

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Copy Files

import shutil

shutil.copy("source.txt", "destination.txt")

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Copy Directories

shutil.copytree("src", "backup")

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Delete Directory

shutil.rmtree("backup")

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Real-World Use

• Backup automation
• File management systems

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6. re (Regular Expressions)

Brief

Used for pattern matching and text processing.

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Common Functions

• findall()
• search()
• match()
• sub()

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Find Pattern

import re

text = "My number is 9876543210"
result = re.findall(r"\d+", text)
print(result)

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Search Pattern

if re.search(r"\d{10}", text):
    print("Valid phone number")

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Replace Text

data = "Python is easy"
print(re.sub("easy", "powerful", data))

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Real-World Use

• Form validation
• Data cleaning
• Log analysis

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7. collections Module

Brief

Provides specialized data structures.

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Counter

from collections import Counter

nums = [1, 2, 2, 3, 3, 3]
print(Counter(nums))

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defaultdict

from collections import defaultdict

d = defaultdict(int)
d["a"] += 1
print(d)

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deque

from collections import deque

dq = deque([1, 2, 3])
dq.appendleft(0)
dq.pop()
print(dq)

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Real-World Use

• Frequency counting
• Queue & stack operations

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8. itertools Module

Brief

Provides fast, memory-efficient iterators.

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count()

from itertools import count

for i in count(1):
    if i == 5:
        break
    print(i)

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cycle()

from itertools import cycle

colors = ["red", "blue"]
for color in cycle(colors):
    print(color)
    break

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combinations()

from itertools import combinations

nums = [1, 2, 3]
print(list(combinations(nums, 2)))