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Introduction to Python

1. First Acquaintance

The Very First Steps Comments Some Simple Math More Challenging Math Challenge Bringing It All Together

2. Variables and Types

Storing Numbers Naming Rules Using Variables Data Types Numbers Challenge Storing Text String Indexing Negative Indexing and Length String Slicing Challenge Concatenation

3. Conditional Statements

Boolean Data Type Challenge: Comparison Operators Combining Conditions Challenge: Logical Operators Membership Operators and Types Comparison Simple if/else Expressions Challenge: Grocery Store Challenge: Odd and Even if/elif/else Expressions Challenge: Grocery Store Extended Challenge: Positive, Negative or Zero

4. Other Data Types

What Is a List?List Methods Challenge Nested Lists Challenge What Is a Tuple?Tuple Methods Challenge Nested Tuples Challenge What Is a Dictionary?Challenge Dictionary Methods Challenge

5. Loops

while Loop Challenge for Loop Challenge Range Challenge Iterating Over Indexes Nested Loops

6. Functions

Built-in Functions Challenge Defining Your First Function Challenge if/else Statements in Functions Challenge Functions With No Return Challenge Modifying Functions Challenge Lambda Functions Challenge

Introduction to Python

Negative Indexing and Length

You can also index from the end of the string. In this case, the last element has an index of -1, the second-to-last is -2, and so on.

Note
Keep in mind that -1 is the go-to way to access the last element.

Now that you're familiar with referencing characters in a string, you might wonder how to determine the total number of characters in that string. Fortunately, Python provides the len() function for that. Just pass the string or the variable holding the string as an argument.

As you might notice, the length of a string corresponds to the number of characters in it. Thus, the total count of characters in a string is always one greater than the index of its last character. For instance, if the length of a string is 10, the index of its last character is 9.