Python quickstart for programmers: Python Kung Fu

1. Python Kung Fu

Beautiful is better than ugly.

Explicit is better than implicit.

Simple is better than complex.

Complex is better than complicated.

Flat is better than nested.

Sparse is better than dense.

Readability counts.

Special cases aren't special enough to break the rules.

Although practicality beats purity.

Errors should never pass silently.

Unless explicitly silenced.

In the face of ambiguity, refuse the temptation to guess.

There should be one-- and preferably only one --obvious way to do it.

Although that way may not be obvious at first unless you're Dutch.

Now is better than never.

Although never is often better than *right* now.

If the implementation is hard to explain, it's a bad idea.

If the implementation is easy to explain, it may be a good idea.

Namespaces are one honking great idea -- let's do more of those!

Prototyping

Glue language

Web development

System administration

Desktop applications

Everything! Ok not everything but almost

print(''Hello world'')

Python 3

print ''Hello World''

Python 2.6

Notice the missing ;

#This is a comment

Numeric

Long or int e.g. 1

Float e.g. 2.5

Complex e.g. 3 + 4j

Boolean

Strings

'I am a string'

Im also a string

Sequences

Lists (or array)[0,1,3] [2,5,woo hoo]

Tuples (1,2,3)

Collections

Dictionary (or hash or map)

{123:mi casa, 234:casa de pepito}

set('hola')

Additional types

unicode, buffer, xrange, frozenset, file

id = 10

Watch out for aliasing!

Cool new stuff

Sorry no ++ or -

The rest is about the same

Including this

+=-=*=/=%=**=//=

y = abs( x )

z = complex( r, i )

from math import *

from math import sqrt

Construction

today = date( 2006, 8, 25 )

Notice the missing 'new'

Methods

which_day = today.weekday()

print "The sum of %d and %d is %f " % (a, b, sum)

print ''The sum of'' + a + '' and '' + b '' is '' + sum

ifvalue < 0:

print 'Im negative'

elif value == 0:

print 'Im zero'

print 'Im positive'

Your usual stuff

str1 = "Abc Def"

str2 = "Abc def"

if str1 == str2 :

print "Equal!!"

else :

print "Not Equal!!"

name1 = "Smith, John";

name2 = "Smith, Jane";

if name1 < name2 :

print "Name1 comes first."

elif name1 > name2 :

print "Name2 comes first."

else :

print "The names are the same."

if "Smith" in name1 :

print name1

# The is operator along with None can tests for null references.

result = name1 is None

result2 = name1 == None

Watch out, ther is no Null!

theSum = 0

while i >> S = [x**2 for x in range(10)]

>>> V = [2**i for i in range(13)]

>>> M = [x for x in S if x % 2 == 0]

# point.py

# Defines a class to represent two-dimensional discrete points.

class Point :

def __init__( self, x = 0, y = 0 ) :

self.xCoord = x

self.yCoord = y

def __str__( self ) :

return "(" + str( self.yCoord ) + ", " +

str( self.yCoord ) + ")"

def getX( self ) :

return self.XCoord

def getY( self ) :

return self.yCoord

def shift( self, xInc, yInc ) :

self.xCoord += xInc

self.yCoord += yInc

from point import *

pointA = Point( 5, 7 )

pointB = Point()

Private

def __helpermethod

def __privatefield

class DerivedClassName(BaseClassName):

Multiple Inheritance

Operator overloading

There are no 'interfaces' but you can emulate them.

There is no 'abstract' or 'virtual' keyword but you can emulate this behaviour.

Abstract base classes serve as THE alternative to interfaces. Python ABC's are somewhat similar to C++ ABC's

Duck typing

function calculate(a, b, c) => return (a+b)*c

example1 = calculate (1, 2, 3)

example2 = calculate ([1, 2, 3], [4, 5, 6], 2)

example3 = calculate ('apples ', 'and oranges, ', 3)

print to_string example1

[1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6]

apples and oranges, apples and oranges, apples and oranges,

Thus, duck typing allows polymorphism without inheritance. The only requirement that function calculate needs in its variables is having the "+" and the "*" methods

myList = [ 12, 50, 5, 17 ]

print myList[ 4 ]

except IndexError:

print "Error: Index out of range."

def min( value1, value2 ) :

if value1 == None or value2 == None :

raise TypeError

if value1 < value2 :

return value1

return value2

Class factories

Function factories

Functional programming

Generators

Advanced list idioms

Tons of other tricks

CPython 2.6 and 3.0

CPython with Psyco

Jython

IronPython

Stackless Python

and more...

Python quickstart for programmers: Python Kung Fu

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