Getting Started with Python: The Basics

Printing

The print() function is your way of communicating with the world. It displays whatever you put inside the parentheses on the screen.

print("Hello, Python!")
print(123)

Basic Data Types: String, Integer, and Float

Think of data types as the different "species" of information Python can handle.

Data Type	Name	Example	Description
String	str	"Nucleaus"	Text wrapped in quotes (single or double).
Integer	int	776	Whole numbers, positive or negative.
Float	float	3.14	Numbers with a decimal point.

name = "NMR Meets Biology" # String
version = 6 # Integer
completed = 0.95 # Float

print(type(name)) # This tells you the type of the variable

Operations on Strings, Integers, and Floats

In Python, the way operators behave depends entirely on the data type you are using. Applying an operator to the wrong type can either result in an error or a surprising result.

---

1. Integer & Float Operations

Both int and float support standard mathematical operators. When you perform an operation between an integer and a float, Python automatically converts the result to a float.

Operator	Description	Example	Result
+	Addition	5 + 2.0	7.0
-	Subtraction	10 - 3	7
*	Multiplication	4 * 3	12
/	Division (always returns float)	10 / 2	5.0
//	Floor Division (removes decimal)	10 // 3	3
%	Modulo (remainder)	10 % 3	1
**	Exponent (Power)	2 ** 3	8

---

2. String Operations

Strings can't do math in the traditional sense, but Python allows "concatenation" and "repetition" using math symbols.

• Concatenation (+): Combines two strings together.

  first = "Python"
  second = "is fun"
  print(first + " " + second)  # Output: Python is fun
  

• Repetition (*): Repeats a string a specific number of times.

  print("Echo! " * 3)  # Output: Echo! Echo! Echo! 
  

3. Type Conversion (Casting)

You cannot "add" a string and a number directly (e.g., "Age: " + 25 will crash). You must convert them first.

age = 25
# Convert int to str to print it with text
print("I am " + str(age) + " years old.") 

# Convert str to int to do math
price_str = "100"
total = int(price_str) + 50  # Output: 150

Pro Tip: When you want to combine variables and strings easily, use f-strings. Just put an f before the quotes and variables in {}: print(f"The total is {total}")

Collections (Lists & Dictionaries)

Sometimes you need to store more than just one piece of data. This is where Lists and Dictionaries come in.

A. Lists

A List is an ordered collection of items. It’s like a shopping list where every item has a specific position (index).

• Note: Python starts counting at 0.

fruits = ["apple", "banana", "cherry"]

print(fruits[0])  # Output: apple
fruits.append("orange") # Adds to the end

B. Dictionaries

A Dictionary stores data in key-value pairs. It’s like a real-life dictionary: you look up a "word" (the key) to find its "definition" (the value).

user = {
    "name": "Alex",
    "age": 25,
    "is_student": True
}

# Accessing a value using its key
print(user["name"]) # Output: Alex

You can iterate over all items inside dictionary:

for k, name in user.items():
    print(k, name)

For Loop

A for loop is used to iterate over a sequence (like a list or a dictionary). It tells Python to "do this action for every item in this collection."

items = ["laptop", "mouse", "keyboard"]

for item in items:
    print(f"Scanning item: {item}")

Functions

Functions are blocks of code that only run when called. They allow you to write logic once and reuse it multiple times, preventing "spaghetti code."

# 'def' starts the function, 'name' is the parameter
def make_uppercase(text):
    return text.upper()

# Calling the function
result = make_uppercase("hello world")
print(result) # Output: HELLO WORLD