Python ---head first

TAb key Offer suggestion on IDLE

Alt p. alt n previous statements,next statement

array

Movies=["abc",12 ]. Can contain mixed type

Print(movies[1])

Movies.insert(1,sth)

movies.append()

for each_movie in movies

print(each_movie)

while condition:

string either double or single quotes

list of list

isinstance(movies,list)-----true

default recurtion limit 1000

BIF built in function

""" triple quotes add comments

a module is a file ends with.py

Pypi

build a module,distribute it, install

def functionname(arg1,arg2=0) default value make second arg optional

if booleanvariable:

All python code associated with name space

_main_

import nester

import os

os.getcwd() //get current directory

os.chdir(). // change directory

data=open('file.txt')

data.seek(0) // go to beginning of the file

for each line in data

print(each line,end=' ')

(v1,v2)=each line.split(":")

(v1,v2)=each line.split(":",1). //split at most to 2 parts

each line.find(":")""" -1 find nothing

data.close()

try:

except:""" when no argument ,all exceptions

Or except ValueError:""" concrete exception

except IOError as err

print(str(err)) """ str() can be used to access the stringed representation of any data object that supports the conversion.

finally:

Two type of list, square brackets, you can change, regular brackets, immutable

in for loop, pass like continue in java

if os.path.exist('stretch.txt')

line.strip()""" trimming

out = open("out.txt", "w")

print("egghkk", file=out)

try:

data=open('file.txt')
except IOError as err:

finally:

if 'data' in locals() """ locals() returns a collection of variables within the current scope

data.close()

try :

with open('file.txt') as data, open('file1.txt') as data2

When you use with,you don't need worry about closing any open files

---

Pickle

Python ships with standard library called picked, which can save and load almost any Python data object. Once you pickle your data to a file, it is persistent and ready to be read into another program at some later data/time. You can store your pickled data on disk, put it in a database, or transfer it over a network.

when you are ready, reversing this process unpickles your persistent pickled data and recreates your data in its original form within Python's memory.

import pickle

...

try:

with open('mydata.pickle', 'wb') as mysavedata:

pickle.dump([1,2,'three'], mysavedata) """ use dump to save

...

with open('mydata.pickle','rb') as myrestoredata:

a_list = pickle.load(myrestoredata) """ restore the data

except pickle.PickleError as perr:

in-place sorting sort()

Copied sorting sorted()

tt.txt looks like this: 2:34,4-45,2.35

def sanitize(time_string):

if '-' in time_string:

splitter = '-'

if ':' in time time_string:

splitter=':'

else:

return (time_string)

(mins,secs) = time_string.split(splitter)

return(mins+'.'+secs)

with open('tt.txt') as file:

data = file.readline()

list = data.strip().split(',')

cleanlist = []

for item in list

cleanlist.append(sanitize(item))

( this whole thing can be written as cleanlist = [sanitize(item) for item in list] )

print(sorted(cleanlist))

list.pop(1) """ get one element from a list

If you try to add a data item to a set

that already contains the data item, Python simply ignores it.

distances = set()

distances = {10.6, 11, 8, 10.6, "two", 7}

Any duplicates in the supplied list of data values are ignored like 10.6

print(sorted(set([sanitize(t) for t in james]))[0:3])

create dictionary

dictionary1 = {}

dictionary1['Name'] = 'John Cleese'

dictionary1['Occupations'] = ['actor', 'comedian', 'writer', 'film producer']

dictionary2 = dict()

dictionary2= {'Name': 'Michael Palin', 'Occupations': ['comedian', 'actor', 'writer', 'tv']}

---------

define a class

class Athlete:

def __init__(self):

# The code to initialize an "Athlete" object.

create instance

a = Athlete()

When Python processes this line of code, it turns the factory function call into

the following call, which identifies the class, the method (which is automatically

set to __init__()), and the object instance being operated on:

( Athlete.__init__(a) is called)

, not only does the __init__() method require self as its first

argument, but so does every other method defined within your class.

what you write,

d = Athlete("Holy Grail")

d.how_big()

Python executes

Athlete.__init__(d, “Holy Grail”)

Athlete.how_big(d)

, if you save your AthleteList class to a file

called athletelist.py, you can import the into your code

using this line of code:

from athletelist import AthleteList

---------

Python comes with its very own web server,

included in the http.server library module

Here are the five lines of code needed to build a web server in Python.

from http.server import HTTPServer, CGIHTTPRequestHandler

port = 8080

httpd = HTTPServer(('', port), CGIHTTPRequestHandler)

print("Starting simple_httpd on port: " + str(httpd.server_port))

httpd.serve_forever()

data_files = glob.glob("data/*.txt")

form_data = cgi.FieldStorage()

Grab all of the form data and put it in a dictionary

athlete_name = form_data['which_athlete'].value """ which_athlete is a radio button

check which radio button is selected

When your CGI script raises an exception, Python arranges for the error

message to display on STDERR (standard error). The CGI mechanism is

programmed to ignore this output because all it wants is the CGI script’s

standard output.

Python’s standard library comes with a CGI tracking

module (called cgitb) that, when enabled, arranges for detailed error

messages to appear in your web browser.

import cgitb

cgitb.enable()

@property

def top3(self):

return(sorted(set([self.sanitize(t) for t in self]))[0:3])

The use of the @property decorator allows the top3() method to appear

like an attribute to users of the class. So, instead of calling the top3()

method like this:

print(yate.u_list(athletes[athlete_name].top3()))

Treat the top3() method as if it was another class attribute, and call it like

this:

print(yate.u_list(athletes[athlete_name].top3))

The standard library string module

includes a class called Template,

which supports simple string substitutions.

The standard library cgi module

provides support for writing CGI scripts.

ƒ The standard library glob module is

great for working with lists of filenames.

The standard library cgitb module,

when enabled, lets you see CGI coding

errors within your browser.

ƒ Use cgitb.enable() to switch on

CGI tracking in your CGI code.

ƒ Use cgi.FieldStorage() to

access data sent to a web server as part

of a web request; the data arrives as a

Python dictionary.

--

Google provides a cross-platform

Android emulator that lets you develop for the phone as needed

http://developer.android.com/sdk/index.html