Intro to Python

The plan

Let’s do something fun!

How about parsing some stats? See http://www.calvin.edu/~stob/data/al0106.csv for Team stats for AL Teams for years 2001-2006

Can we write enough Python to answer some questions about the data?

Setup

• Get a browser and a terminal window open.
• Install Python 2.7 and IPython
• pick a text editor

Running a command line program

• Editing, saving, running Python code in a file
• working interactively in IPython

Downloading a file from the internet

• Using urllib interactively
• The file type - .read(), .readlines()

Exercise 1

Write a program that downloads a url and prints its contents.

Sample run

$ python myprogram.py http://www.calvin.edu/~stob/data/al0106.csv
... lots of output ....

Sample code for accessing the command line:

import sys

url = sys.argv[-1]
print url

Basic types

• int and float and simple math
• str type and list type, interation and indexing
• converting types in Python

Exercise 2

Read a file url from the command line and:

1. break your file contents apart into a list of strings

2. print the number of lines in the list

3. print the list

More about Types

Let’s explore list and str a little more thoroughly

More about Lists

Everything about lists: indexes and slices, methods, and mutability.

Strings

A lot like lists (indexing/slicing, looping)

But different too. split/join and "stringy" methods.

Immutability!

Exercise 3

Make a list of just the home runs hit. Print it out.

Extra credit: print the total number of homeruns. See sum - but watch out for strings! Sample output:

$ python myprogram.py http://www.calvin.edu/~stob/data/al0106.csv
169
212
...
====
xxxx (Total)

The dict Type

• dictionaries: key/value stores
• indexing by key
• iterating
• the in operator (works on strings and lists too!)

Exercise 4

Make a dictionary with team’s home run totals. Print it out.

BONUS: print out the team with the highest home run total.

$ python myprogram.py http://www.calvin.edu/~stob/data/al0106.csv
{'DET': 988, 'NYY': 1337,
 ... snip ...}