Play with Python

Lab1

هامة قاعدة المعامل في مفاهيم أي ،المحاضرة في الشرح كل :

المعمل قبل المحاضرة في مغطاه ستكون

التمرين من المطلوب شرح فقط المطلوب

ينطلقون ودعهم

Agenda

• Setup the Environment and Hello World

• Exercise 1: o Factorial then Factorial with list

• Exercise 2:

o character count and histogram

• Fun:

o Plot!

Setup the Environment

• Install Python 2.7.3:

o python-2.7.3.msi

• Install Aptana IDE: o Aptana_Studio_3_Setup_3.2.0.exe

Setup the Environment

1- Open your Python IDLE from:

Start >> All Programs >> Python 2.7 >>

IDLE

2- Write your first program:

print "Hello World"

Press Enter

Setup the Environment (Your first project)

3- Start Aptana:

Start >> All Programs >> Aptana Studio 3

press ok for the workspace

4- Create your first project:

Select File >> New >> Project ... >> PyDev Project

5-Enter Project Name: lab1

6-(for first time only) Click on "Please configure an interpreter ... "

7- click auto Config

8- click ok

9- then ok (wait till Aptana finishes ...)

10-create your main file by:

right click on "lab1" in Package Explorer >> New >> PyDev Module

11- Enter Name: main

12- click ok

Screenshots (steps 3- 12)

Setup the Environment (Your first project)

Write the following code in your main file:

n = 5

for i in range(1, n):

print "Hello World"

click on run as from the toolbar

Select "Python Run "

Click Ok (See the run in Console)

Setup the Environment (Your first project)

put your previous code in a function like this

def main():

n = 5

for i in range(1, n):

print "Hello World"

then call it:

main()

Setup the Environment (Your first project)

again change your main to return 2 values, "hello world"

string and its length

def main():

s = "Hello World"

return "Hello World", len(s)

then print the return of main like this:

print main()

('Hello World', 11)

Exercise 1

Write this program in your main file:

def count_char(str):

d = {}

for char in str:

if char in d:

d[char] += 1

else:

d[char] = 1

return d

print count_char("My name is FCIS tell me every thing you know

!")

{' ': 9, 'C': 1, 'F': 1, 'I': 2, 'M': 1, 'S': 1, 'a': 1, 'e': 5, 'g': 1, 'i': 2, 'h': 1, 'k': 1, 'm': 2, 'l': 2, 'o': 1,

'n': 3, 's': 1, 'r': 1, 't': 2, 'w': 1, 'v': 1, 'y': 2}

This program counts the occurrences of characters in given string and returns a

dictionary containing for every key character an integer value

Exercise 1 (10 minutes)

Add a new function draw_historgram() that draws an ascii histogram of a given dictionary (from count_char()) like this:

a : * *

: * * * * * * * * *

e : * * * * *

d : *

g : *

i : * *

M : *

k : *

v : *

m : * * * *

l : * *

o : * *

...

Exercise 1 (Solution)

def draw_historgram(d):

for char in d:

print char, " : ",

for c in range(1, d[char]+1):

print "*",

print ""

Exercise 2

Write this program in your main file:

def fact(n):

if (n <= 1):

return 1

else:

return n * fact(n - 1)

print fact(5)

120

this program computes a factorial for a given integer

Exercise 2 (15 minutes)

Modify this function to make it return the factorial, and also

a list contains all factorials so far like this:

print fact(5)

(120, [1, 2, 6, 24, 120])

the list contains all the factorials from 1 to 5

Exercise 2 (Solution)

def fact(n):

if (n <= 1):

return 1, [1]

else:

prev_fact, theList = fact(n - 1)

current_fact = n* prev_fact

theList.append(current_fact)

return current_fact, theList

print fact(5)

Note: in this exercise the student should be able to implement the solution with the multiple return values ( tuple), this

python feature is explained in the lecture

This exercise is to let the students think the in new way of programming, to feel change from C/C++/C3/Java traditional

languages

Have Fun

Install Pythonxy:

(Click yes for every question the installer asks about

existing python setup)

Open Spyder by:(Start>>python(x,y) >> Spyder >> Spyder

)

Copy and paste your Fact() function to the python

interpreter, and plot Fact() like this:

f, l = fact(5)

plot(l)

Thank You