Documentation / References

• Python Full Documentation– http://docs.python.org/index.html

• Python Quick Reference– http://rgruet.free.fr/

• IPython– <object>?– help <object>– tab completion

Basics• Tabbing is crucial and mandatory

– DO NOT mix tabs with spaces, choose one method and stick to it• Comments:

– # single line comment– """ long comment """

• Philosophic mindset– Shorter and simpler is better, without getting cryptic– Intuitive to existing programmers– No deliberate way to do the same code in two different ways

• Keywords– None– True– False– pass

Duck Typing• “when I see a bird that walks like a duck and swims like a duck and quacks like a duck, I call that

bird a duck.” - James Whitcomb Riley

• Casting:– int(variable)

• int('FF', 16) == 255– float(variable)

• also definable by adding a period– str(variable)

• Type Comparison– type(variable) == type([])– type(variable) == type(“”)– type(variable) == type(0)

Static Typing

C/C++/C#Java

Duck Typing (Dynamic)

Python

Dynamic Typing

PerlPHPRuby

Data Types

• Modules• Objects– Integer– Float– Strings– List– Dictionary– Tuple

• Decorators• Generators

Modules

• Two methods of importing• import math– Now, functions or attributes defined in math can be

accessed like so: math.pi, math.sin(), etc.• from math import *– Now, all of math is imported into the global

namespace and can be accessed like so: pi, sin(), etc.• from math import pi– Now, only pi is in the global namespace

Numbers• Types:

– Integers– Floats

• Infinite length• Math

– ( + - * / % ^ & | )– ** instead of ^ (but ^ exists as XOR, be careful)– += exists, but ++ does not (use +=1)

• More math– import math– math.e, math.pi, math.cos(), math.acos(), math.cosh(), math.log(),

math.ceil(), math.sqrt()

Control Flow Statements• if, elif, else… and, or, not• while

– continue– break

• for– More like foreach in other languages

• try, except

list = [2, 3, 1, 7]for x in list: print "output:”, str(x)

output: 2output: 3output: 1output: 7

try: dict_array[0]['item’] # code for successexcept IndexError: # code if [0] failsexcept KeyError: # code if ['item'] fails

if len(dict_array) == 0: # code if [0] failselif dict_array.has_key('item‘): # code if ['item'] failselse: # code for success

list = [2, 3, 1, 7]i = 0while i < len(list): print "output:", str(i) i += 1

output: 2output: 3output: 1output: 7

switch Control Structure

• There isn’t one.• Alternatives to switch:– if, elif, else

– dictionary forms

if var == 'one': # do 'one' specific codeelif var == 'two': # do 'two' specific codeelif var == 'three': # do 'three' specific codeelse: # do default code

def one_code(): # do 'one' specific codedef two_code(): # do 'two' specific codedef three_code(): # do 'three' specific codedef default_code(): # do default code{'one': one_code, 'two': two_code, 'three': three_code}[var]()

{'one': lambda x: x+1, 'two': lambda x: x+2, 'three': lambda x: x+3}[var](var)

Strings

• Defined in usual ways• Important Methods:– strip()– join()– split()

• String formatting (like printf)

mystr = " first second third"myarr = mystr.strip().split(" ")

for i in xrange(0, len(myarr)): print "output:", myarr[i]

print "mystr::%s::" % " ".join(myarr)

output: firstoutput: secondoutput: thirdmystr::first second third::

Lists

• Important methods– append()– extend()– insert()– pop()

list = [3, 4, 5]print "pop: %d" % list.pop(1)

list.insert(0, 2)list.append(6)list.extend([7, 8])

print "list: %s" % str(list)

pop: 4list: [2, 3, 5, 6, 7, 8]

Slicing

• A more complex way of handling list items and strings

list = [2, 3, 1, 7, 5]

print listprint list[1:2]print list[2:]print list[-2:]print list[:-2]

[2, 3, 1, 7, 5][3][1, 7, 5][7, 5][2, 3, 1]

Tuple

• Collection of a fixed amount of values• Tuple unpacking

def output_three_multiples(self, number): return (number*2, number*3, number*4)

(first,second,_) = output_three_multiples(7)

File Manipulation

• First thing that made me like Python

file = open("filename", "r")contents = file.readlines()file.close()

line_num = 1for line in contents: print "%d: %s" % (line_num, line) line_num += 1

file = open("filename", "r")contents = file.read()file.close()

print contents

Classes• Everything involving classes in Python is weird• All classes extend "object"

– Like Java– Historically this was not the case, so be careful

• Constructor is: def __init__(self):• Private methods prefixed with two underscores• Static methods use @staticmethod decorator• Super methods are weird, too

Class Codeimport attrdictimport errorsfrom execute import *

class server(attrdict): def __init__(self, dict): super(server, self).__init__(dict)

# no executer until a function makes one self.executer = None

def __do_execute(self, cmd): ret = self.require_remote() if ret: return (None,None,None)

if self.executer: return self.executer.execute(cmd) else: return execute_srv(self.remote_server, cmd)

def require_remote(self): if not self.require_dict(self.remote_server, [ "ip", "port" ]): return errors.throw(errors.BACKEND_INVALID_INPUT)

Class Code 2import errors, glob, serverfrom execute import *

class master(server): def __init__(self, dict): super(master, self).__init__(dict)

@staticmethod def __do_execute(cmd): return execute(cmd)

def remove_key(self): ret = self.require_remote() if ret: return ret

# strip keys from remote server (exit_code,_,_) = self.__do_execute( "ssh -i %s " % glob.config.get("paths", "master_private_key") + "-p " + str(self.remote_server['port']) + " root@" + self.remote_server['ip'] + " " + "\"sed -r \\\"/^.*_panenthe$/d\\\" -i %s\"" % glob.config.get("paths", "user_ssh_authorized_keys") )

# fail if exit_code != 0: return errors.throw(errors.SERVER_REMOTE_REMOVE)

# return return errors.throw(errors.ERR_SUCCESS)

LibrariesName Function

Tkinter TK graphics

os POSIX functions & operating system generic functions

re Regular expressions (close to PCRE)

sys Information about current instance and system (I.E. arguments to command line, exit(), etc.)

urwid curses/ncurses frontend with common widgets