for (int i=0; i < container.size(); ++i)
    {
        // Do stuff
    }

    my_container = ['Larry', 'Moe', 'Curly']
    index = 0
    for element in my_container:
        print ('{} {}'.format(index, element))
        index += 1

    my_container = ['Larry', 'Moe', 'Curly']
    for index, element in enumerate(my_container):
        print ('{} {}'.format(index, element))

Every programming language has its own idioms. Programming language idioms are nothing more than the generally accepted way of writing a certain piece of code. In Python, for example, there are many ways to write code that loops over the elements of a list. You could write:

        i = 0
        while i < len(my_list):
            # do stuff...
            i += 1
            

This would work just fine. But it's not idiomatic (or "Pythonic"). The idiomatic version is:

for i in my_list: 

OK, But Why Should I Care?

Consistently writing idiomatic code has a number of important benefits:

• Others can read and understandyour code easily
• Others can maintain and enhance your code with minimal effert
• Your code will contain fewer bugs
• Your code will teach others to write correct code without any effort on your part

Sounds great, but I'm new to Python. How do I learn to write idiomatic code?

This was always the toughest part. Previously, the only ways to learn idiomatic Python were to

• Read existing code (but how do you know if it's idiomatic?)
• Get feedback during a code review (which only helps if you're working with others, you do code reviews, and they know what is idiomatic)
• Buy a general book on the language (which may use idioms, but probably won't point them out or explain why they're important)

There should be an easier way!

There is! Writing Idiomatic Python contains the most common and important Python idioms in a format that maximizes identification and understanding. Each idiom is presented as a recommendation to write some commonly used piece of code (like the for loop above). It is followed by an explanation of why the idiom is important. It also contains two code samples: the "Harmful" way to write it and the "Idiomatic" way.

• The "Harmful" way helps you identify the idiom in your own code.
• The "Idiomatic" way shows you how to easily translate that code into idiomatic Python.