01-python-basics.md

Python Cheatsheets, vol.1: Introduction to the Anaconda very basics

Python provides a versatile set of tools for programming beginners. Mastering the basics, including comments, variables, math operators, and functions, sets the foundation for more advanced coding concepts. Keep exploring, practicing, and building to enhance your Python skills!

As the first part of our Introduction, we'll focus on the following learning path for our cheatsheets:

1. Basic syntax and data types (integers, floats, and strings).
2. Variables and assignements.

Let'sss go!

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Table of Contents

1. 📝 Comments
   • Inline Comments
   • Multiline Comments
   • Comments in Code
2. 📊 Variables
   • Variable Naming Rules
3. ➕➖✖️➗ Math Operators
   • Addition
   • Subtraction
   • Multiplication
   • Division
   • Expression Examples
   • More Examples
4. 🔄 Augmented Assignment Operators
   • Increment and Decrement
   • Examples
5. 🦄 Walrus Operator
   • Assignment within Expressions
   • Examples
6. 🎲 Data Types
   • Integers
   • Floating-point Numbers
   • Strings
7. 🧬 Concatenation and Replication
   • String Concatenation
   • String Replication
8. 🔄 Functions
   • Defining Functions
   • Calling Functions
9. 🖨️ The print() Function
   • Basic Usage
   • The end Keyword
   • The sep Keyword
10. 📥 The input() Function
    • User Input
    • Default Message
    • Formatted Strings
11. 📏 The len() Function
    • Evaluating Length
    • Test of Emptiness
12. 🏛 License

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📝 Comments

Comments in Python are used to explain code and make it more readable. They can be inline or multiline.

Inline Comments

An inline comment is a comment on the same line as a statement. It is indicated by the # symbol.

# This is an inline comment
result = 1  # initialization

Multiline Comments

Multiline comments are used for longer explanations. They start and end with three single quotes (''').

'''
This is a
multiline comment
'''

Comments in Code

Comments can also be added to the end of a line of code.

result = 1  # initialization

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📊 Variables

In Python, variables are used to store data values. Variables are created when they are assigned a value.

Variable Naming Rules

1. It can be only one word.

name = 'John'
# valid

full_name = 'John Doe'
# valid

2. It can use only letters, numbers, and the underscore (_) character.

user_age = 25
# valid

user@age = 25
# invalid

3. It can’t begin with a number.

var_23 = 'hello'
# valid

23_var = 'hello'
# invalid

4. Variable names starting with an underscore (_) are considered as "unuseful".

_secret_code = '12345'
# valid

_ = 'This variable is not used'
# valid but discouraged

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➕➖✖️➗ Math Operators

Math operators perform operations on numeric values. They include addition (+), subtraction (-), multiplication (*), and division (/).

Addition

The addition operator (+) adds two numbers.

result = 2 + 3
# 5

Subtraction

The subtraction operator (-) subtracts the right operand from the left operand.

result = 5 - 2
# 3

Multiplication

The multiplication operator (*) multiplies two numbers.

result = 3 * 4
# 12

Division

The division operator (/) divides the left operand

by the right operand.

result = 8 / 2
# 4.0

Expression Examples

Expressions can include multiple operators and operands. The order of operations is followed.

result = 2 + 3 * 6
# 20

result = (2 + 3) * 6
# 30

result = 2 ** 8
# 256

result = 23 // 7
# 3

result = 23 % 7
# 2

result = (5 - 1) * ((7 + 1) / (3 - 1))
# 16.0

More Examples

a = 10
b = 3

sum_result = a + b
# 13

difference_result = a - b
# 7

product_result = a * b
# 30

division_result = a / b
# 3.333...

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🔄 Augmented Assignment Operators

Augmented assignment operators combine an arithmetic operation with variable assignment. They perform the operation and assign the result to the variable.

Increment and Decrement

Increment and decrement are common operations where a variable's value is increased or decreased by 1.

count = 0
count += 1  # Increment by 1
# count is now 1

total = 5
total *= 2  # Multiply by 2
# total is now 10

Examples

value = 10

value += 5
# value is now 15

value -= 3
# value is now 12

value *= 2
# value is now 24

value /= 3
# value is now 8.0

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🦄 Walrus Operator

The Walrus Operator (:=) allows assignment of variables within an expression while returning the value of the variable.

Assignment within Expressions

message := "Python Basics"
# 'Python Basics'

is_true = True
print(result := "Success") if is_true else print("Failure")
# Success

print(name := "John")
# John

The Walrus Operator, or Assignment Expression Operator, was firstly introduced in 2018 via PEP 572 and then officially released with Python 3.8 in October 2019.

Note

PEP 572 provides the syntax, semantics, and examples for the Walrus Operator.

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🎲 Data Types

Data types specify the type of values that variables can hold. In Python, the main data types are integers, floating-point numbers, and strings.

Integers

Integers are whole numbers without a fractional part.

integer_number = 42
negative_integer = -10

Floating-point Numbers

Floating-point numbers are numbers with a decimal point or in exponential form.

float_number = 3.14
negative_float = -0.5

Strings

Strings are sequences of characters, enclosed in single or double quotes.

text = 'Hello, Python!'
multiline_text = """This is a multiline
string in Python."""

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🧬 Concatenation and Replication

String concatenation combines two strings, while string replication repeats a string multiple times.

String Concatenation

result = 'Python' + ' Basics'
# 'Python Basics'

String Replication

phrase = 'I love ' + 'Python! ' * 3
# 'I love Python! I love Python! I love Python! '

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🔄 Functions

Functions are blocks of reusable code. They receive input, perform actions, and return output.

Defining Functions

Functions are defined using the def keyword, followed by the function name, parameters, and a colon.

def greet(name):
    """
    This function greets the user.
    """
    print(f"Hello, {name}!")

Calling Functions

Functions are called by using the function name followed by parentheses and passing any required arguments.

greet('Alice')
# Hello, Alice!

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🖨️ The print() Function

The print() function writes the value of the argument(s) it is given. It handles multiple arguments, floating-point quantities, and strings.

Basic Usage

print('Greetings!', 'Welcome', 'to Python Basics!')
# Greetings! Welcome to Python Basics!

The end Keyword

The end keyword can be used to avoid the newline after the output or end the output with a different string.

phrase = ['printed', 'with', 'a', 'dash', 'in', 'between']
for word in phrase:
    print(word, end='-')
# printed-with-a-dash-in-between-

The sep Keyword

The sep keyword specifies how to separate objects if there is more than one.

print('cats', 'dogs', 'mice', sep=', ')
# cats, dogs, mice

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📥 The input() Function

The input() function takes input from the user and converts it into a string.

User Input

name = input('What is your name? ')
print(f'Hi, {name}!')

Default Message

fav_language = input('What is your favorite programming language? ')
print(f'Nice choice! {fav_language}')

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📏 The len() Function

The len() function evaluates to the integer value of the number of characters in a string, list, dictionary, etc.

Evaluating Length

string_length = len('Python Basics')
# 13

list_length = len([1, 2, 3, 4, 5])
# 5

Note

Test of emptiness of strings, lists, dictionaries, etc., should not use len as it prefers direct boolean evaluation.

Test of Emptiness

my_list = [1, 2, 3]

# bad
if len(my_list) > 0:
    print("This list is not an empty one!")

# good
if my_list:
    print("This list is not an empty one!")

⬆ Back to Index

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🏛 License

Although I am the owner of the examples provided (always taking into account previous examples that I got to know during my formation, of course), I would want to send some huge thanks to Olivia Redanz for her fantastic illustration! Oh, and remember that you can make the Dinosaur extremely happy if you...

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