Pi Maker

Workshop

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3.Pi for Python

Mayank Joneja

Python Basics

The “Pi” in Raspberry Pi stands for Python, a popular

high level language

Start installing Python on your PC

If you know C then this is a much easier and intuitive

language

Most of the codes we write here are in Python

The only reason to perhaps use C/C++ with regards to

Raspberry Pi based applications could be for running

code faster as the kernel and assembler all are in C

However Python in most of the cases is good enough

for reducing the length of code by a factor of 10 or

more

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The Zen of Python

The core philosophy of the

language is summarized by the

document “PEP 20 –The Zen of

Python”

https://www.youtube.com/watch?

v=tKTZoB2Vjuk (Nick Parlante

Google Developer Python Classes)

www.codecademy.com

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Namaste Duniya

Start Python in command line console

print “Namaste Duniya”

# is for single line comments, ‘’’ ‘’’ for multi-line comments

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Arithmetic and Algebra

print 2+2

print “two plus two equals”, 2+2

print 10/2

print 2*4

print 4-2

22/7 (default int)

22.0/7

a = 2

b = 3

C = 6

print a+b+C

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Strings

a = “Raspberry”

b = “Pi”

c = “Rules”

print a,b,c

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Conditionals

We’ll be dealing a lot with these when we start with GPIO as well

temperature = float(input(‘What is the temperature in deg C ?’))

if temperature > 35:

print (‘Wear Shorts!’)

else:

print (‘Wear trousers’)

print ‘Get some exercise outside’

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Lets get loopy

#While Loop

n = 0

while (n<=10):

print n

n+=1 #or n = n+1

#For Loopfor n in range (0,10):

print n

for n in range (0,10+1)

print n

for n in range (0,10,2):

print n

for n in range (10,0,-1):

print n

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Random

import random

print (random.randint(10,40))

import random

for n in range (1,6+1):

print(random.randint(10,40)

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Lists (Mutable arrays)

mytext = [“I”, “Love”, “My”, “Raspberry”, “Pi”]

for n in range(0,5):

print (mytext[n])

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Input and output

var = raw_input(“Enter something: ”)

print “you entered ”, var

#raw_input() reads every input as a string

#then its up to the user to process the string

str1 = raw_input(“Enter anything”)

print “raw_input = ” , str1

#input() actually uses raw_input() and then #tries to convert the input data to a number using eval()

x = input(“Enter a number”)

print “input= “, x

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Line Break

test = raw_input(“Input word”)

print “Why “ + test + “ there a line break every time?”

#add a newline to the end for testing

test = test + ‘/n’

#simple way to remove a trailing newline

if ‘\n’ in test:

test = test[:-1]

print “Why” + test + “ there a line break every time?”

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Illustrate input and print

applicant = raw_input(“Enter applicant’s name”)

supervisor = raw_input(“Enter supervisor’s name”)

time = input(“Enter time”)

print “interview will be at”, time, ”by”, supervisor, “for”, applicant

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Function definition

def happyBirthdaySalman():

print “Happy Birthday dear Salman!”

def happyBirtthdayAishwarya():

print “Happy Birthday dear Aishwarya!”

happyBirthdaySalman()

happyBirthdayAishwarya()

def happyBirthday(person):

print “Happy Birthday “ + person + “.”

happyBirthday(‘Salman’)

happyBirthday(‘Aishwarya’)

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Running Python on the Pi

We’ll use Nano quite often for editing files on the Pi. Such a command line tool (vim, nano)

is used to edit the files that can’t be accessed in r/w mode through Samba, for e.g. some

.conf files or other system files

Make sure that you don’t use a module name as the name for your script. eg. random.py

We’ll be using sudo to launch the editor for such files in order to run them as root user

But for most scripts, we can use any text editor on our laptop, (I prefer to use Sublime Text)

and then transfer the files on to the Pi in our Project directory through Samba

Then in order to run the script:

sudo python filename.py