teaching beginning programming with Python
[![/space/python-new.png](/space/python-new.png)](http://python.org/)[![/space/python-old.png](/space/python-old.png)](http://python.org/)

I'm
a software engineer. I've been programming for a long time - in
[school](http://www.stanford.edu/), at [work](http://google.com/), and for
[fun](/space/software). While I was in school, I also taught computer science as
a TA for three years.

I TAed a [mid-level class](http://cs107.stanford.edu/), though, so by the time I
met the students, they didn't just know how to program, they'd also mastered
more in-depth concepts like pointers, recursion, computer architecture, and
algorithms.

Last Sunday, for the first time, I had the chance to teach someone to program
who'd never written a line of code before. It was very, very different from
TAing. It was also a _lot_ of fun.

I was inspired by [David Bau](http://davidbau.com/)'s [Haaarg,
world!](http://davidbau.com/archives/2005/07/29/haaarg_world.html), so I decided
to use [Python](http://python.org/) because of its simple syntax, plain-english
keywords, and interactive shell. We started in the shell with a few **print**
statements.

    >>> print 'hi'
    hi
    >>> print 3
    3
    >>> print 2 + 2
    4
    >>> print 'hi', 2
    hi 2

We quickly covered strings, integers, and basic arithmetic. We opened a .py file
and wrote a Python script, ran it, saw the output, and cheered. Hello, world!

    print 'Hello, world!'

We moved on to variables, which we thought about as little boxes in memory, with
names, that could hold things. We used **input()** to ask the user's name,
stored it in a variable, and said hi. We did more arithmetic, this time with
variables instead of integer constants.

Variables were a little tricky, but not too bad. Even better, they were the
worst of it. String operations, expressions, conditionals, loops, and other
control flow came easily. Even libraries and import statements didn't cause much
trouble.

Other than variables, the only speed bump was = for assignment vs. == for
equality testing. It's tough for first-timers to understand why they need to use
different operators. Guido actually mentioned this himself in one of his article
about teaching with Python. I tried to find a link, but no such luck.

In the end, we had a working copy of that old standard, the number guessing
game. Check it out!

    import random
    play\_again='Y'

    while play\_again=='Y':
        print "pick a number"
        answer=random.randint(0,100)
        guess=input()
        num\_guesses=1
        while guess!=answer:
            num\_guesses=num\_guesses+1
            if guess<=answer:
                print "higher than ", guess
            if guess>=answer:
                print "lower than ", guess
            if guess>=answer-2 and guess<=answer+2:
                print "almost"
            guess=input()

        print "great! The correct number was ", answer
        print "your number of guesses was ", num\_guesses
        print "play again? 'Y'/'N'"
        play\_again=input()