Python Essentials: From First Commands to Custom Functions - Part 2

This is Part 2 of the series. Read Part 1 first.

In the journey of becoming a professional developer—whether you're aiming for Django backend development, AI automation, or Data Science—the goal isn't just to write code that works. The goal is to write code that is Pythonic: short, readable, elegant, and clear.

This guide dives into the logic of conditionals, the efficiency of Pythonic expressions, and the structural power of the new match statement.

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1. Logic and Conditionals: Making Decisions

Conditionals are the brain of your script. They allow your code to choose between different paths based on specific situations.

The Toolkit: Conditional Operators

To compare values, Python uses a standard set of operators:

Choosing Your Structure: if vs. if-elif-else

A common "real-life bug" occurs when developers use multiple if statements instead of an if-elif chain.

The "Asking 3 Teachers" Problem (Multiple ifs):

If you use only if statements, Python checks every single one, even if the first one was already true.

marks = 85
if marks >= 50: print("Pass")      # ✅ Prints
if marks >= 70: print("Good")      # ✅ Prints
if marks >= 80: print("Excellent") # ✅ Prints
# Result: Three separate messages for one grade.

The "Decisive Teacher" Solution (if-elif):

In an if-elif chain, Python stops as soon as it finds the first True condition. Order matters here: always check the strictest or highest condition first.

marks = 85
if marks >= 80:
    print("Excellent") # ✅ Prints and STOPS.
elif marks >= 70:
    print("Good")
else:
    print("Fail")

Logical Alternatives: or vs. and

• or Operator: Returns True if at least one condition is true. Perfect for checking alternatives (e.g., if role == "admin" or role == "editor").
• and Operator: Returns True only if both conditions are true. Use this for specific ranges (e.g., checking if a number falls between 10 and 20).

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2. The Art of Pythonic Expressions

"Pythonic" code uses built-in features to avoid unnecessary variables and repetitive logic. It looks natural, almost like reading English.

Comparison: ❌ Non-Pythonic vs. ✅ Pythonic

Functions and Implicit Returns

Instead of writing a full if-else inside a function to return a Boolean, remember that a comparison is already an expression that evaluates to True or False.

# ❌ Instead of this:
def even(n):
    if n % 2 == 0: return True
    else: return False

# ✅ Do this:
def even(n):
    return n % 2 == 0

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3. Structural Pattern Matching: The match Statement

Introduced in Python 3.10, match is the cleaner, more powerful sibling of if-elif. While if-elif is like asking many yes/no questions, match is like picking a specific option from a menu.

When to use match

Use it when comparing one variable against many fixed patterns, such as API Request Handling (GET, POST, PUT, DELETE) or Command Line Tools.

command = input("Enter command: ")
match command:
    case "start":
        print("Starting service...")
    case "stop":
        print("Stopping service...")
    case "restart" | "reload": # Using | as 'or'
        print("Restarting...")
    case _: # The "Default" case (if nothing matches)
        print("Unknown command")

Advanced Power: Unlike switch statements in other languages, Python's match can "unpack" data. For example, case ("login", username): can extract the username directly from a tuple.

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4. Professional Standards: The "Bug-Free" Checklist

In Python, indentation and the colon (:) are not optional—they are compulsory parts of the syntax. As you write, always ask yourself:

• Readability: Can someone else understand this in 5 seconds?
• Efficiency: Can I get the computer to ask fewer questions (e.g., using elif or match instead of multiple ifs)?
• Bugs: Am I checking for the right Boolean values (True/False with capital letters)?

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Previous in the Series

👈 Python Essentials: From First Commands to Custom Functions - Part 1 — Covers terminal basics, data types, string formatting, and writing clean functions.