Course Content

Introduction to Python (dev copy)

1. First Acquaintance with Python

The Very First Steps in Python How to Use Comments for Readability Perform Simple Math in Python Handle More Challenging Math in Python Bringing Python Fundamentals Together

2. Variables and Types in Python

How to Store Numbers in Python Python Naming Rules for Variables How to Work with Variables in Python Data Types in Python Challenge: Converting Kilometers to Miles Store Text with Strings in Python String Indexing in Python Negative Indexing and String Length in Python String Slicing in Python Challenge: Retrieving Letters from String String Concatenation in Python

3. Conditional Statements in Python

Boolean Data Type in Python Challenge: Working with Comparison Operators How to Combine Conditions in Python Challenge: Working with Logical Operators Membership Operators and Type Comparisons in Python How to Use if/else Expressions in Python Challenge: Running a Grocery Store Challenge: Creating Odd and Even Logic if/elif/else Expressions Challenge: Running Grocery Store Extended Challenge: Outputting Positive, Negative or Zero

4. Other Data Types in Python

Python Lists Common List Methods in Python Challenge: Updating List Nested Lists in Python Challenge: Retrieving Information from Nested List Python Tuples Common Tuple Methods in Python Challenge: Updating Tuple Nested Tuples in Python Challenge: Retrieving Information from Nested Tuple Python Dictionaries Challenge: Completing Dictionary Common Dictionary Methods in Python Challenge: Updating Dictionary

5. Loops in Python

Explore the while Loop in Python Challenge: Working with the While Loop Explore the for Loop in Python Challenge: Working with the For Loop Range Function in Python Challenge: Using the Range Function How to Iterate Over Indexes in Python Explore Nested Loops in Python

6. Functions in Python

Built-in Functions in Python Challenge: Converting Heights How to Create Functions in Pythons Challenge: Writing First Function Use of if/else Statements in Python Functions Challenge: Identifying Positive Values Functions Without Return in Python Challenge: Creating Logging Function Modifying Functions in Python Challenge: Updating Logic of the Function Lambda Functions in Python Challenge: Creating Lambda Function

if/elif/else Expressions

In our last example, you might've picked up on the fact that we didn't account for when the revenue is exactly $2000. In such a scenario, we're neither at a loss nor making a profit. So, we should tweak our code to handle such nuances.

To check a subsequent condition after your initial check, use elif. The structure goes like this:

python

The code following the final else will run only if none of the previous conditions are met.

Recall our previous example about string length. Let's adjust it. Now, we'll label a string as 'large' if it contains more than 20 characters, 'medium' if it has more than 10 (but certainly no more than 20), and 'small' for anything less.


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# Assign some medium string
test = "medium string"

# Conditional statements
if len(test) > 20:
    print("String: '", test, "' is large")
elif len(test) > 10:
    print("String: '", test, "' is medium")
else:
    print("String: '", test, "' is small")
    
# One more checking
test = "small"

# Conditional statement
if len(test) > 20:
    print("String: '", test, "' is large")
elif len(test) > 10:
    print("String: '", test, "' is medium")
else:
    print("String: '", test, "' is small")

Note

You can stack multiple elif blocks as required. However, it's good to note that overusing elif blocks isn't the most efficient way to structure your code.

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Section 3. Chapter 9