Python Basics

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17 December 2024 - 2 mins read time
Tags: Study Guide Python Software

Basics

Control Flow

if 1 == 1:
    print("1 is equal to 1")
elif 1 == 2:
    print("1 is equal to 2")
else:
    print("1 is not equal to 1 or 2")

Loops

for i in range(0, 10):
    print(i)

i = 0
while i < 10:
    print(i)
    i += 1

Functions

def add(a, b):
    return a + b

List Comprehension

squares = [x**2 for x in range(5)]  # [0, 1, 4, 9, 16]

Lambda function

square = lambda x: x**2
print(square(5))   # 25

Map

nums = [1, 2, 3]
squared = list(map(lambda x: x**2, nums))   # [1, 4, 9]

Filter

evens = list(filter(lambda x: x % 2 == 0, nums))  # [2]

Data Structures

List

list = [1, 2, 3, 4, 5]
list.append(6)
list.pop()
list[0]

Bit Strings

bit_str = "1011"
hex_val = hex(int(bit_str, 2))[2:]

Tuple

tuple = (1, 2)
x, y = tuple

Dictionary

dictionary = {"key": "value"}
dictionary["new_key"] = "new_value"
dictionary.pop("key")
dictionary["key"]

Set (unique elements)

set = {1, 2, 3, 4, 5}
set.add(6)
set.remove(1)

Algorithms

Efficient Sorting

list = [1, 2, 3, 4, 5]
sorted_list = sorted(list)
list.sorted()

Classes

class Car:
    def __init__(self, brand, model):
        self.brand = brand
        self.model = model

    def drive(self):
        return f"{self.brand} {self.model} is driving."

# Create object
my_car = Car("Tesla", "Model S")
print(my_car.drive())   # Tesla Model S is driving.

Files

Read file

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

Write file

with open("file.txt", "w") as file:
    file.write("Hello, File!")

Exceptions

try:
    result = 10 / 0
except ZeroDivisionError as e:
    print("Cannot divide by zero:", e)
finally:
    print("Cleanup")

Input and Output

Standard Input

# Single-line input
name = input("Enter your name: ")
print(f"Hello, {name}!")

# Multiple inputs in one line
x, y = map(int, input("Enter two numbers: ").split())
print(f"x: {x}, y: {y}")

# Multiple lines of input
lines = []
while True:
    line = input("Enter a line (or 'exit' to stop): ")
    if line == "exit":
        break
    lines.append(line)
print(lines)

Standard Ouput

# Print with formatting
name, age = "Alice", 30
print(f"{name} is {age} years old.")  # Using f-strings

# Print without newline
print("Hello", end=" ")
print("World")  # Output: Hello World

# Print to file
with open("output.txt", "w") as file:
    print("Writing to file!", file=file)

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