Getting started
Basic concepts: taking our first steps
Using an IDE
Objects and classes
Loops, ranges, and iterators
Working with files
Exception handling
Python data types
Course project: building a TODO application
And now what?

Variable naming

In my examples, I’ve picked the general name result, but you can choose any name you deem appropriate. As a general rule, always pick a variable name that best describes its contents. This practice makes your code more readable and easy to understand, not just for others, but also for future you. Trust me when I say that, if you read back your own code a few weeks or months later, you’ll be surprised at how much effort it requires you to grasp what’s going on.

If we were calculating the total price of a shopping cart here, for example, a good name would be shopping_cart_total.

Don’t skimp on the number of characters in your variable names. It’s better to have clean, readable names like shopping_cart_total instead of an abbreviation like sct. Even total is probably too short, because you’ll need to spend time finding of what the total is calculated. As you’ll soon learn, a good code editor auto-completes things like variable names, so you don’t have to type them in completely, if that’s what you’re worried about.

Valid Python variable names

Some characters are not allowed in a variable name; there are a few rules we need to abide by. Let’s start with the complete list of valid characters that can appear in a variable name:

  • Lowercase and uppercase letters: a-z and A-Z
  • Numbers: 0-9
  • Underscores: _

Additionally, there are these two rules:

  • Variable names must start with a letter or the underscore character, and can not start with a number.
  • Names are case-sensitive

Here are some valid variable names:

  • name_1,
  • name_2,
  • _database_connection

These are invalid names:

  • 1tomany (don’t start with a number)
  • my-number (- is not allowed)
  • my number (spaces are not allowed)

And these variables are not the same, due to case sensitivity:

  • cartTotal
  • carttotal

A note on camel-case

This is for those that come from another programming language, like C# or Java. Many programming languages make use of camel-case to name variables. With camel-case, we use uppercase letters to more clearly separate words.

In Python, we can use camel-case, but we prefer underscores for variable names. So instead of shoppingCartTotal, we Pythonistas use shopping_cart_total. However, camel-case is the norm for class names. If you don’t know what that means, don’t worry, we’ll get to those later on.