Master Python Conditionals and Loops: A Visual Guide to If, While, For

Python Conditional Statements

Python conditional statements decide which code block to execute based on the truth value (True or False) of one or more expressions.

The execution process can be understood through the following diagram:

In Python, any non‑zero and non‑empty value is considered true; 0 or null is false.

The basic if statement syntax is:

If the condition evaluates to true, the indented block following it is executed. An optional else block runs when the condition is false.

Typical comparison operators include >, <, ==, >=, and <=. Multiple conditions can be combined using and or or, and parentheses control precedence.

Because Python lacks a switch statement, multiple branches are handled with elif. The or operator succeeds if any condition is true; and requires all conditions to be true.

Python While Loop Statements

The while loop repeatedly executes a block as long as its condition evaluates to true.

The condition can be any expression; non‑zero or non‑empty values are true. When the condition becomes false, the loop ends.

Example execution result:

Two important statements can modify loop flow: continue skips the current iteration, while break exits the loop entirely.

Infinite Loop

If a loop condition is always true, the loop runs indefinitely. The following example demonstrates an infinite while loop, which can be stopped with CTRL+C:

Loop Using Else Statement

In Python, for … else and while … else execute the else block only when the loop finishes normally (i.e., not terminated by break).

Python For Loop Statements

The for loop iterates over any sequence such as a list or string.

Flowchart:

Example output:

Iterating by Index

Another way to traverse a sequence is by index using len() and range():

Python break Statement

The break statement terminates the nearest enclosing loop, similar to its use in C.

Example output:

Python continue Statement

The continue statement skips the rest of the current loop iteration and proceeds to the next one.

Example output:

Python pass Statement

The pass statement is a null operation used as a placeholder where syntactically a statement is required.

Example output: