All Courses
Python Basics

Python Variables & Printing

1. The print() Function (Deep Dive)

Printing Multiple Values

  • Pass multiple arguments separated by commas
  • print() automatically adds a space between them
print("hello", 5, True)   # hello 5 True

The Newline Character \n

  • By default, every print() ends with \n (newline character)
  • \n is invisible but tells the console to move to the next line
  • That's why each print() call appears on a new line
print("hello")   # internally prints: hello\n
print("Tim")     # internally prints: Tim\n

The end Keyword Argument

  • Overrides what gets printed at the end of the statement
  • Default is end="\n" — change it to keep output on the same line
print("hello", 5, True, end=" | ")   # hello 5 True |
print("Tim")                          # Tim
# Output: hello 5 True | Tim

print("hello", end="world")  # helloworld (no newline)

end only affects that specific print() call

2. Variables

What is a Variable?

  • A named container that stores a value
  • Lets you access and manipulate data throughout your program
  • Similar to variables in math (e.g. x = 1)

Defining a Variable

x = 3           # stores integer 3
y = "hello"     # stores string "hello"
  • Convention: one space on each side of =

Accessing a Variable

print(x)   # 3
print(y)   # hello

Variables Storing Other Variables

  • Assigning one variable to another copies the value at that moment
  • Changing the original later does not affect the copy
x = 3
y = "hello"
num = y          # num = "hello" (copies y's current value)
y = x            # y is now 3, but num is still "hello"

print(num)       # hello
print(y)         # 3

Order of Execution

  • Python runs code top to bottom, line by line
  • A variable's value at any point is whatever was last assigned above that line
x = 3
y = "hello"
print(x)    # 3
print(y)    # hello  ← y hasn't been reassigned yet at this point
num = y
y = x
print(num)  # hello
print(y)    # 3
x = 4
print(x)    # 4

3. Variable Naming Rules

Rule Valid Invalid
Must start with a letter or _ name, _name 1name, @name
Can contain letters, numbers, _ name2, max_score name 2, name@2
No spaces allowed max_score max score
No special characters user_name user!name, user#name
Case sensitive name ≠ Name —

4. Naming Conventions

Use Meaningful Names

name = "Tim"          # ✅ clear purpose
max_score = 10        # ✅ clear purpose
x1 = "Tim"            # ❌ unclear purpose

Snake Case vs Camel Case

max_score = 10    # ✅ snake_case — preferred in Python
maxScore = 10     # ❌ camelCase — used in other languages, avoid in Python

Avoid Starting with Uppercase

  • Classes in Python start with uppercase — naming variables with uppercase can cause confusion
Name = "Tim"    # ❌ avoid — looks like a class
name = "Tim"    # ✅ correct

5. Accessing Undefined Variables

  • Using a variable that hasn't been defined causes a NameError
print(nam)   # NameError: name 'nam' is not defined

Always read the error message — it shows the line number and what went wrong

6. Key Takeaways & Recap

  1. print() can take multiple comma-separated values — auto-adds spaces
  2. Every print() ends with \n by default — use end= to change this
  3. A variable is a named container storing a value
  4. Assigning a = b copies b's value at that moment — later changes to b don't affect a
  5. Code executes top to bottom — order matters
  6. Variable names: start with letter/_, no spaces/special chars, case-sensitive, use snake_case