Python¶

Catherine Devlin
APCUG 2013 Regional Conference
Sep 15, 2013
http://tinyurl.com/apcug-2013-python-intro

A buzzword-enhanced language¶

Open-source
Multi-purpose
Multi-platform
Dynamic
Object-oriented
Highly readable

What's it look like?¶

In [11]:

target_letter = "r"
for animal in ["horse", "cat", "racoon", "duck"]:
    if target_letter in animal:
        print(animal + " contains the letter " + target_letter)
    else:
        print("sorry, no " + target_letter + " in " + animal)

horse contains the letter r
sorry, no r in cat
racoon contains the letter r
sorry, no r in duck

Familiar terms¶

for, if, else, etc.

Dynamic¶

In [43]:

def lots_of(x):
    return 3 * x

stuff = "milk "
print(type(stuff))
print(lots_of(stuff))
stuff = 3
print(type(stuff))
print(lots_of(stuff))

<class 'str'>
milk milk milk 
<class 'int'>
9

In [38]:

import datetime

print(lots_of(datetime.datetime.now()))

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-38-61e691416648> in <module>()
      1 import datetime
      2 
----> 3 print(lots_of(datetime.datetime.now()))

<ipython-input-37-3b437fd333c5> in lots_of(x)
      1 def lots_of(x):
----> 2     return 3 * x
      3 
      4 print(lots_of("milk"))
      5 print(lots_of(3))

TypeError: unsupported operand type(s) for *: 'int' and 'datetime.datetime'

Significant whitespace¶

In [12]:

target_letter = "r"
for animal in ["horse", "cat", "racoon", "duck"]:
    if target_letter in animal:
        print(animal + " contains the letter " + target_letter)
    else:
        print("sorry, no " + target_letter + " in " + animal)

horse contains the letter r
sorry, no r in cat
racoon contains the letter r
sorry, no r in duck

No line endings (a line ending is a line ending)
Indentation marks blocks
Python interpreter == your eyeball!

Highly readable¶

In [1]:

target_letter = "r"
for animal in ["horse", "cat", "racoon", "duck"]:
    if target_letter in animal:
        print(animal + " contains the letter " + target_letter)
    else:
        print("sorry, no " + target_letter + " in " + animal)

horse contains the letter r
sorry, no r in cat
racoon contains the letter r
sorry, no r in duck

Object-oriented¶

In [13]:

animal = "moose"
animal.upper()

Out[13]:

'MOOSE'

In [3]:

class Animal(object):
    def eat(self, food):
        return "What yummy " + food + "!"
       
fido = Animal()
fido.eat('dog food')

Out[3]:

'What yummy dog food!'

Inheritence¶

In [4]:

class Cat(Animal):
    def purr(self):
        return 'rrrrrrrrrrrrrrrr'

agamemnon = Cat()
agamemnon.eat('hotdish')

Out[4]:

'What yummy hotdish!'

In [5]:

agamemnon.purr()

Out[5]:

'rrrrrrrrrrrrrrrr'

In [6]:

fido.purr()

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-6-32f565adf250> in <module>()
----> 1 fido.purr()

AttributeError: 'Animal' object has no attribute 'purr'

Introspection¶

In [29]:

help("x".upper)

Help on built-in function upper:

upper(...)
    S.upper() -> str
    
    Return a copy of S converted to uppercase.

In [30]:

dir("x")

Out[30]:

['__add__',
 '__class__',
 '__contains__',
 '__delattr__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__getitem__',
 '__getnewargs__',
 '__gt__',
 '__hash__',
 '__init__',
 '__iter__',
 '__le__',
 '__len__',
 '__lt__',
 '__mod__',
 '__mul__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__rmod__',
 '__rmul__',
 '__setattr__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 'capitalize',
 'casefold',
 'center',
 'count',
 'encode',
 'endswith',
 'expandtabs',
 'find',
 'format',
 'format_map',
 'index',
 'isalnum',
 'isalpha',
 'isdecimal',
 'isdigit',
 'isidentifier',
 'islower',
 'isnumeric',
 'isprintable',
 'isspace',
 'istitle',
 'isupper',
 'join',
 'ljust',
 'lower',
 'lstrip',
 'maketrans',
 'partition',
 'replace',
 'rfind',
 'rindex',
 'rjust',
 'rpartition',
 'rsplit',
 'rstrip',
 'split',
 'splitlines',
 'startswith',
 'strip',
 'swapcase',
 'title',
 'translate',
 'upper',
 'zfill']

Handy collections: lists¶

In [32]:

hotdish_ingredients = ["noodles", "tuna", "mayo", "celery"]
shopping_list = ["apple", "bread", hotdish_ingredients, "spinach"]

for buy_me in shopping_list:
    print(buy_me)

apple
bread
['noodles', 'tuna', 'mayo', 'celery']
spinach

Handy collections (2): dictionaries¶

In [34]:

german = {"cat": "Katze", dog: "Hund"}
german["cat"]

Out[34]:

'Katze'

list comprehension¶

In [3]:

name = "American of Personal Computer User Groups"
initials = [letter for letter in name if letter.isupper()]
print(initials)
abbrev = "".join(initials)
print(abbrev)

['A', 'P', 'C', 'U', 'G']
APCUG

Rich standard library¶

formats: csv, json, xml.*...
compression: zlib, zipfile, tarfile, bz2...
datastores: dbm, shelve, pickle...
network: ftplib, urllib2, smtp, SimpleHTTPServer...
cryptography: hashlib
user interfaces: cmd, curses...

PyPI (the Cheese Shop)¶

http://pypi.python.org

34,000 + freely available modules

Libraries make tasks easy¶

In [4]:

import requests

response = requests.get('http://dma1.org')
response.status_code

Out[4]:

In [5]:

response.content[:100]

Out[5]:

b'<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">\n<HTML>\n<HEAD>\n  <LINK REL="SHORTCUT '

In [15]:

import re
re.search(">(APCUG.*?)<", str(response.content)).group(1)

Out[15]:

'APCUG 2013 Regional Computer Conference'

What's it used for?¶

web development
scientific programming
data analysis
GUI tools
systems administration
games

Education¶

Youth: "Python for Kids" books, classes
College: MIT
Professionals: Universal "pidgin"

How's it used?¶

Socially!¶

Developed by distributed groups
Code submitted to PyPI
PyCon, PyOhio...

How to learn it¶

https://wiki.python.org/moin/BeginnersGuide
http://docs.python-guide.org
http://learnpython.org
Coursera
PyOhio
Python Workshop for Women
catherine.devlin@gmail.com
tinyurl.com/apcug-2013-python-intro