Control Flow in Python: 3 Essential Tools

Control flow in programming determines the order in which statements are executed. In Python, you have three powerful tools at your disposal: if statements, for loops, and while loops. By mastering control flow, you can create programs that adapt to different situations, make decisions, and repeat actions, making your code truly dynamic.

1. If Statements: Making Decisions

If statements are the foundation of decision-making in Python. They allow your code to take different paths based on conditions. The basic structure is:

a = True
if a:
  print("It is true")
else:
  print("It is false")

• if: The condition to check. If True, the indented block below is executed.
• else: (Optional) The block to execute if the if condition is False.

Indentation Matters: The indented lines under the if and else are part of their respective blocks. Python uses indentation to define blocks of code.

Nested If Statements: You can have if statements inside other if statements, creating more complex decision trees.

a = True
b = True
if a:
  if b:
    print("Both are true") 

2. For Loops: Iterating Over Sequences

For loops are used to iterate over sequences like lists, strings, or tuples. They execute a block of code for each item in the sequence.

my_list = [1, 2, 3, 4, 5]
for item in my_list:
    print(item)

• for item in my_list: The loop variable (item) takes on each value from my_list in turn.
• The indented block is executed once for each item.

3. While Loops: Looping Based on Conditions

While loops are used when you want to repeat a block of code as long as a condition is true. They are useful when you don’t know in advance how many iterations are needed.

a = 0
while a < 5:
    print(a)
    a = a + 1 

• while a < 5: The condition is checked before each iteration. As long as it’s true, the loop continues.
• Incrementing: It’s important to include code that eventually makes the condition false to avoid infinite loops.

Key Difference: While loops are condition-based, while for loops iterate over sequences.

Frequently Asked Questions (FAQ)