Comprehensive Python Basics: Syntax, Data Structures, File I/O, Functions, OOP, Exceptions, Math, Regex, File System, and Network Requests

Basic Syntax

Printing, variable assignment, arithmetic, conditionals, loops, and simple data processing examples.

print("Hello, World!")

message = "Hello, Python!"
print(message)

a = 5
b = 3
sum = a + b
print(sum)

num = 10
if num > 0:
    print("Positive")
else:
    print("Not Positive")

for i in range(1, 11):
    print(i)

i = 1
while i <= 10:
    print(i)
    i += 1

numbers = [1, 2, 3, 4, 5]
total = sum(numbers)
print(total)

def is_palindrome(s):
    return s == s[::-1]
s = "madam"
print(is_palindrome(s))

s = "hello, world!"
print(s.upper())

s = "hello, world!"
if "world" in s:
    print("Substring found")
else:
    print("Substring not found")

Data Structures

Lists, dictionaries, loops, sorting, and set operations.

my_list = []
my_list.append(1)
my_list.append(2)
my_list.append(3)
print(my_list)

my_dict = {}
my_dict['name'] = 'Alice'
my_dict['age'] = 30
print(my_dict)

my_list = [1, 2, 3, 4, 5]
for item in my_list:
    print(item)

my_dict = {'name': 'Alice', 'age': 30}
for key, value in my_dict.items():
    print(f"{key}: {value}")

my_list = [3, 1, 4, 1, 5, 9]
my_list.sort()
print(my_list)

my_list = [3, 1, 4, 1, 5, 9]
print(max(my_list))
print(min(my_list))

my_list = [1, 2, 3, 4, 5]
my_list.remove(3)
print(my_list)

list1 = [1, 2, 3]
list2 = [4, 5, 6]
combined_list = list1 + list2
print(combined_list)

my_set = set()
my_set.add(1)
my_set.add(2)
my_set.add(3)
print(my_set)

my_tuple = (1, 2, 3)
print(my_tuple[0])
print(my_tuple[1])
print(my_tuple[2])

File Operations

Reading, writing, appending, line‑by‑line processing, copying, counting words, and replacing text.

with open('file.txt', 'r') as file:
    content = file.read()
    print(content)

with open('file.txt', 'w') as file:
    file.write('Hello, World!')

with open('file.txt', 'a') as file:
    file.write('
Appending new line.')

with open('file.txt', 'r') as file:
    for line in file:
        print(line.strip())

with open('source.txt', 'r') as source_file:
    with open('destination.txt', 'w') as dest_file:
        dest_file.write(source_file.read())

with open('file.txt', 'r') as file:
    content = file.read()
    words = content.split()
    print(len(words))

with open('file.txt', 'r') as file:
    content = file.read()
new_content = content.replace('old_word', 'new_word')
with open('file.txt', 'w') as file:
    file.write(new_content)

import csv
with open('data.csv', 'r') as csvfile:
    reader = csv.reader(csvfile)
    for row in reader:
        print(row)

import csv
with open('data.csv', 'w', newline='') as csvfile:
    writer = csv.writer(csvfile)
    writer.writerow(['Name', 'Age'])
    writer.writerow(['Alice', 30])
    writer.writerow(['Bob', 25])

import json
with open('data.json', 'r') as f:
    data = json.load(f)
    print(data)

Functions and Modules

Defining functions, default arguments, *args, **kwargs, and importing modules.

def greet(name):
    print(f"Hello, {name}!")
greet("Alice")

def add(a, b):
    return a + b
result = add(3, 5)
print(result)

def greet(name="World"):
    print(f"Hello, {name}!")
greet()
greet("Alice")

def sum_all(*args):
    return sum(args)
result = sum_all(1, 2, 3, 4, 5)
print(result)

def display_info(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")
display_info(name="Alice", age=30)

import math
result = math.sqrt(16)
print(result)

# mymodule.py

def hello():
    print("Hello from mymodule!")

import mymodule
mymodule.hello()

from math import sqrt
result = sqrt(16)
print(result)

import sys
for arg in sys.argv:
    print(arg)

import os
current_dir = os.getcwd()
print(current_dir)

Object‑Oriented Programming

Classes, inheritance, class/instance/static methods, properties, and special methods.

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def greet(self):
        print(f"Hello, my name is {self.name} and I am {self.age} years old.")
person = Person("Alice", 30)
person.greet()

class Animal:
    def speak(self):
        pass
class Dog(Animal):
    def speak(self):
        print("Woof!")
class Cat(Animal):
    def speak(self):
        print("Meow!")
dog = Dog()
cat = Cat()
dog.speak()
cat.speak()

class Circle:
    pi = 3.14159
    def __init__(self, radius):
        self.radius = radius
    def area(self):
        return Circle.pi * (self.radius ** 2)
circle = Circle(5)
print(circle.area())

class Rectangle:
    def __init__(self, width, height):
        self.width = width
        self.height = height
    def area(self):
        return self.width * self.height
rectangle = Rectangle(5, 10)
print(rectangle.area())

class MathUtils:
    @staticmethod
    def add(a, b):
        return a + b
result = MathUtils.add(3, 5)
print(result)

class Person:
    count = 0
    def __init__(self, name):
        self.name = name
        Person.count += 1
    @classmethod
    def get_count(cls):
        return cls.count
person1 = Person("Alice")
person2 = Person("Bob")
print(Person.get_count())

class BankAccount:
    def __init__(self, balance):
        self.__balance = balance
    def deposit(self, amount):
        self.__balance += amount
    def withdraw(self, amount):
        if amount <= self.__balance:
            self.__balance -= amount
        else:
            print("Insufficient funds")
    def get_balance(self):
        return self.__balance
account = BankAccount(1000)
account.deposit(500)
account.withdraw(200)
print(account.get_balance())

class Temperature:
    def __init__(self, celsius):
        self.celsius = celsius
    @property
    def fahrenheit(self):
        return (self.celsius * 9/5) + 32
temp = Temperature(25)
print(temp.fahrenheit)

class Temperature:
    def __init__(self, celsius):
        self._celsius = celsius
    @property
    def celsius(self):
        return self._celsius
    @celsius.setter
    def celsius(self, value):
        self._celsius = value
    @property
    def fahrenheit(self):
        return (self._celsius * 9/5) + 32
temp = Temperature(25)
print(temp.fahrenheit)
temp.celsius = 30
print(temp.fahrenheit)

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y
    def __str__(self):
        return f"Point({self.x}, {self.y})"
    def __repr__(self):
        return f"Point(x={self.x}, y={self.y})"
point = Point(3, 4)
print(point)
print(repr(point))

Exception Handling

Try/except blocks, multiple exceptions, finally, and raising errors.

try:
    result = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero")

try:
    result = 10 / 0
except (ZeroDivisionError, TypeError):
    print("An error occurred")

try:
    result = 10 / 0
except ZeroDivisionError as e:
    print(f"Error: {e}")
try:
    result = 10 / 2
except ZeroDivisionError:
    print("Cannot divide by zero")
finally:
    print("This will always execute")

def divide(a, b):
    if b == 0:
        raise ValueError("Cannot divide by zero")
    return a / b
try:
    result = divide(10, 0)
except ValueError as e:
    print(e)

Mathematical and Scientific Computing

Square roots, powers, circle area, factorial, and combinations.

import math
result = math.sqrt(16)
print(result)

result = pow(2, 3)
print(result)

import math
def circle_area(radius):
    return math.pi * (radius ** 2)
area = circle_area(5)
print(area)

import math
result = math.factorial(5)
print(result)

import math
result = math.comb(5, 2)
print(result)

String Operations

Concatenation, formatting, splitting, joining, replacing, searching, case conversion, trimming, slicing, and length.

first_name = "John"
last_name = "Doe"
full_name = first_name + " " + last_name
print(full_name)

name = "Alice"
age = 30
message = f"Name: {name}, Age: {age}"
print(message)

text = "apple,banana,orange"
fruits = text.split(',')
print(fruits)

fruits = ['apple', 'banana', 'orange']
text = ','.join(fruits)
print(text)

text = "Hello, World!"
new_text = text.replace("World", "Python")
print(new_text)

text = "Hello, World!"
index = text.find("World")
print(index)

text = "Hello, World!"
upper_text = text.upper()
lower_text = text.lower()
print(upper_text)
print(lower_text)

text = "   Hello, World!   "
trimmed_text = text.strip()
print(trimmed_text)

text = "Hello, World!"
substring = text[7:12]
print(substring)

text = "Hello, World!"
length = len(text)
print(length)

Regular Expressions

Email, phone, date matching, substitution, and pattern checking.

import re
text = "Contact us at [email protected] or [email protected]"
emails = re.findall(r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}', text)
print(emails)

import re
text = "Call us at 123-456-7890 or 987-654-3210"
phone_numbers = re.findall(r'\b\d{3}[-.]?\d{3}[-.]?\d{4}\b', text)
print(phone_numbers)

import re
text = "Meeting on 2023-10-05 and 2023-10-10"
dates = re.findall(r'\b\d{4}-\d{2}-\d{2}\b', text)
print(dates)

import re
text = "The quick brown fox jumps over the lazy dog"
new_text = re.sub(r'fox', 'cat', text)
print(new_text)

import re
text = "123-456-7890"
pattern = r'\b\d{3}[-.]?\d{3}[-.]?\d{4}\b'
if re.match(pattern, text):
    print("Match found")
else:
    print("No match")

File and Directory Operations

Creating, deleting, listing, copying, moving, renaming, checking existence, size, modification time, recursive traversal, searching, compression, and extraction.

import os
os.makedirs('new_directory', exist_ok=True)

import shutil
shutil.rmtree('directory_to_delete')

import os
for item in os.listdir('path/to/directory'):
    print(item)

import shutil
shutil.copy('source_file.txt', 'destination_file.txt')

import shutil
shutil.move('source_file.txt', 'destination_directory/')

import os
os.rename('old_name.txt', 'new_name.txt')

import os
if os.path.exists('file.txt'):
    print('File exists.')

import os
file_size = os.path.getsize('file.txt')
print(f'File size: {file_size} bytes')

import os
mod_time = os.path.getmtime('file.txt')
print(f'Modified time: {mod_time}')

import os
for root, dirs, files in os.walk('path/to/directory'):
    for name in files:
        print(os.path.join(root, name))

import os
for root, dirs, files in os.walk('path/to/directory'):
    if 'target_file.txt' in files:
        print(os.path.join(root, 'target_file.txt'))

import zipfile
with zipfile.ZipFile('archive.zip', 'w') as zipf:
    zipf.write('file.txt')

import zipfile
with zipfile.ZipFile('archive.zip', 'r') as zipf:
    zipf.extractall('extracted_directory')

import csv
with open('data.csv', 'r') as csvfile:
    reader = csv.reader(csvfile)
    for row in reader:
        print(row)

import csv
with open('data.csv', 'w', newline='') as csvfile:
    writer = csv.writer(csvfile)
    writer.writerow(['Name', 'Age'])
    writer.writerow(['Alice', 30])
    writer.writerow(['Bob', 25])

Network Requests

GET, POST, custom headers, file download/upload, JSON and XML handling, timeout, error handling, and sessions.

import requests
response = requests.get('https://api.example.com/data')
print(response.text)

import requests
payload = {'key': 'value'}
response = requests.post('https://api.example.com/submit', data=payload)
print(response.text)

import requests
headers = {'Content-Type': 'application/json'}
response = requests.get('https://api.example.com/data', headers=headers)
print(response.text)

import requests
url = 'https://example.com/file.zip'
response = requests.get(url)
with open('downloaded_file.zip', 'wb') as f:
    f.write(response.content)

import requests
files = {'file': open('file.txt', 'rb')}
response = requests.post('https://api.example.com/upload', files=files)
print(response.text)

import requests
response = requests.get('https://api.example.com/data')
data = response.json()
print(data)

import requests
import xml.etree.ElementTree as ET
response = requests.get('https://api.example.com/data.xml')
root = ET.fromstring(response.text)
for child in root:
    print(child.tag, child.attrib)

import requests
response = requests.get('https://api.example.com/data', timeout=5)
print(response.text)

import requests
try:
    response = requests.get('https://api.example.com/data')
    response.raise_for_status()
except requests.exceptions.HTTPError as errh:
    print("Http Error:", errh)
except requests.exceptions.ConnectionError as errc:
    print("Error Connecting:", errc)
except requests.exceptions.Timeout as errt:
    print("Timeout Error:", errt)
except requests.exceptions.RequestException as err:
    print("OOps: Something Else", err)

import requests
session = requests.Session()
session.auth = ('username', 'password')
response = session.get('https://api.example.com/data')
print(response.text)