paladique/python-part1-template

CS140: Computer Science Seminar - Python Starter Template

Welcome to this Python starter template 🚀 to supercharge your Python skills! We will use this template for class notes. This README covers practical tips and sample code snippets for variables, strings, integers, booleans, functions, and logical operations.

Table of Contents

• Variables
• Strings
• Integers
• Booleans
• Functions
• If Statements

Variables

Variables store data values. A variable is created the moment you first assign a value to it.

Tips:

• Use meaningful variable names to make your code more readable.
• Python is dynamically typed, which means you can reassign variables to different data types.

x = 5
x = "Hello"  # Now x is of type str

Strings

Strings in Python represents text. Strings are enclosed in double quotes "".

Tips:

• Use the + operator to concatenate strings directly.
• For better performance and readability, especially with multiple strings, consider using the .join() method.

Using the + operator

greeting = "Hello"
name = "Alice"
sentence = greeting + ", " + name + "!"
print(sentence)  # Outputs 'Hello, Alice!'

Using the join method for multiple parts

words = ["Hello", "world", "from", "Python"]
sentence = " ".join(words)
print(sentence)  # Outputs 'Hello world from Python'

You can also:

• Trim spaces with strip()
• Find substrings with find() or in
• Replace parts of strings with replace()
• Here are some quick examples to get you started:

phrase = "   Hello, world!   "
trimmed = phrase.strip()
print(trimmed)  # Outputs 'Hello, world!'

Checking for a substring

contains_world = "world" in trimmed
print(contains_world)  # Outputs True

Replacing text

updated_phrase = trimmed.replace("Hello", "Goodbye")
print(updated_phrase)  # Outputs 'Goodbye, world!'

Integers

In Python, an integer is a whole number, positive or negative, without decimals of unlimited length.

Creating an integer

my_int = 10
print(my_int)  # Outputs 10

Converting an integer to a string

my_str = str(my_int)
print(my_str)  # Outputs '10'

Converting a string to an integer

new_int = int(my_str)
print(new_int)  # Outputs 10

Booleans

Booleans represent one of two values: True or False. Boolean expressions are often used in conditional statements and loops.

Tips:

• Use Boolean expressions directly in conditions without explicit comparison operators.

flag = True
if flag:
    print("Flag is True")

Functions

Functions in Python are defined using the def keyword. They organize code into manageable blocks, making your programs easier to write and read.

Tips

• Keep it short and sweet: Aim for functions that perform a single task. This makes them easier to test, understand, and reuse.
• Use descriptive names: Function names should be descriptive enough to convey their purpose. For example, calculate_total() is more informative than func1().
• Limit the number of arguments: Ideally, functions should have a few arguments. If you find yourself needing more, consider whether your function is doing too much or if you should use a class to encapsulate the data.

A simple function with a return statement

def get_message():
    return "Hello, world!"

message = get_message()
print(message)  # Outputs 'Hello, world!'

A function with arguments but no return value

def print_sum(x, y):
    print("The sum is:", x + y)

print_sum(5, 3)  # Outputs 'The sum is: 8'

A function with arguments and a return value

def multiply_numbers(a, b):
    return a * b

result = multiply_numbers(4, 3)
print(result)  # Outputs 12

If Statements

Tips:

• Use clear conditions: Make your conditions straightforward and easy to understand.
• Avoid unnecessary nesting: Where possible, keep your if statements flat. Deeply nested if statements can make your code hard to read and maintain.
• Use elif for multiple conditions: If you have several conditions that are mutually exclusive, elif can be a cleaner alternative to multiple if statements.
• Combine conditions with logical operators: Use and, or, and not to combine conditions, making complex decisions easier to manage.

Simple if statements

age = 18
if age >= 18:
    print("You are an adult.")

x = 10
if x > 5 and x < 15:
    print("x is between 5 and 15")

if not x > 20:
    print("x is not greater than 20")

Using if-else statement

temperature = 20
if temperature > 25:
    print("It's warm outside.")
else:
    print("It's not warm outside.")