Python Training at VMWare Bangalore - Day¶

Sep 18-20 2017 Vikrant Patil

These notes are available online at http://notes.pipal.in/2017/vmware-python

Quick start to python¶

1

1

1.2

1.2

x = 3

x

3

print(x)

3

name = "krishna"

print(name)

krishna

raga = input()

asawary

print(raga)

asawary

Integers¶

2 + 2

4

2 - 3

-1

2 * 3

6

2 ** 3

8

9 % 2

1

2 ** 100

1267650600228229401496703205376

2 ** 1000

10715086071862673209484250490600018105614048117055336074437503883703510511249361224931983788156958581275946729175531468251871452856923140435984577574698574803934567774824230985421074605062371141877954182153046474983581941267398767559165543946077062914571196477686542167660429831652624386837205668069376

5 // 2

2

5 / 2

2.5

Floting point numbers¶

0.0001 + 1

1.0001

Strings¶

first = "Rupali"
second = "Rupak"

print(first, second)

Rupali Rupak

"Rupali" "Rupak"

'RupaliRupak'

name = "Rupali" "Rupak"

name

'RupaliRupak'

first + second

'RupaliRupak'

name = first + " " + second

name

'Rupali Rupak'

five = str(5)

five

'5'

star = "*"

fivestar = star * 5

fivestar

'*****'

print("*"*50)

**************************************************

It also supports usual escape chars

twolines = "first line \n second line"

print(twolines)

first line 
 second line

columns = "column1\tcolumn2"

print(columns)

column1	column2

multiline = """
pthon is very simple
python is very powerfull
python is very close to human language , english
and it has nothing do with snakes, but it is related 
BBC's monty python show
"""

multiline

"\npthon is very simple\npython is very powerfull\npython is very close to human language , english\nand it has nothing do with snakes, but it is related \nBBC's monty python show\n"

print(multiline)

pthon is very simple
python is very powerfull
python is very close to human language , english
and it has nothing do with snakes, but it is related 
BBC's monty python show

print("\u0c85")

ಅ

print("I can have ' single quote inside")

I can have ' single quote inside

print('I can have " double quote inside')

I can have " double quote inside

'something'

'something'

It has binary data

binary = b'binary'

print(binary)

b'binary'

hex(5)

'0x5'

hex(ord("b"))

'0x62'

binary = b'\x62\x69\x6e'

print(binary)

b'bin'

High level data type called lists

letters = ['a','b','c']

letters

['a', 'b', 'c']

letters[0]

'a'

letters[1]

'b'

len(letters)

3

ones = [1,1,1,1]

moreones = ones + ones

moreones

[1, 1, 1, 1, 1, 1, 1, 1]

multidata = ["a", 1, "Three", ones]

multidata

['a', 1, 'Three', [1, 1, 1, 1]]

multidata[0]

'a'

multidata[2]

'Three'

multidata[3]

[1, 1, 1, 1]

multidata[0] = "b"

multidata

['b', 1, 'Three', [1, 1, 1, 1]]

topten = list(range(10))

topten

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

topten[-1]

9

topten[-2]

8

topten[:2]

[0, 1]

topten[2:]

[2, 3, 4, 5, 6, 7, 8, 9]

topten[5:7]

[5, 6]

someotherlist = ['a', 'b','c','d','e']

someotherlist[0]

'a'

someotherlist[2:4]

['c', 'd']

someotherlist[1:4:2]

['b', 'd']

someotherlist[1:4:-1]

[]

someotherlist[4:0:-1]

['e', 'd', 'c', 'b']

len(someotherlist)

5

someotherlist[1:4][-1]

'd'

someotherlist[::-1]

['e', 'd', 'c', 'b', 'a']

matrix

matrix = [[1,2,3], [2,3,4],[5,6,7]]

matrix

[[1, 2, 3], [2, 3, 4], [5, 6, 7]]

matrix[0]

[1, 2, 3]

matrix[-1]

[5, 6, 7]

matrix[0][-1]

3

There is a sibling of list caleed tuple. tuple is just like list, but immutable.

point = (1.1, 2.0)

point[0]

1.1

point[1]

2.0

traingle = ((0,0),(0,1),(1,1))

traingle[0]

(0, 0)

traingle[0] = (0,3)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-101-4a7f9c0e226e> in <module>()
----> 1 traingle[0] = (0,3)

TypeError: 'tuple' object does not support item assignment

ones = (1,1,1)

ones + ones

(1, 1, 1, 1, 1, 1)

ones

(1, 1, 1)

ones + ones

(1, 1, 1, 1, 1, 1)

mutable = list(ones)

mutable

[1, 1, 1]

mutable[0] = 0

mutable

[0, 1, 1]

ones

(1, 1, 1)

Dictionaries are named collection of objects. You retrive objects aby names instead of index

machine = {"name":"mozart", "os":"ubuntu", "make":"acer"}

machine

{'make': 'acer', 'name': 'mozart', 'os': 'ubuntu'}

machine['name']

'mozart'

machine['os']

'ubuntu'

machine["key"] = 5

machine

{'key': 5, 'make': 'acer', 'name': 'mozart', 'os': 'ubuntu'}

machine

{'key': 5, 'make': 'acer', 'name': 'mozart', 'os': 'ubuntu'}

set :Python has datatype set which allows us to store data as a set.

paragraph = """
I have random fiction
written for this trp aining
and we want to find how many english charecters are used in it
"""

set(paragraph)

{'\n',
 ' ',
 'I',
 'a',
 'c',
 'd',
 'e',
 'f',
 'g',
 'h',
 'i',
 'l',
 'm',
 'n',
 'o',
 'p',
 'r',
 's',
 't',
 'u',
 'v',
 'w',
 'y'}

set([2,2,3,4,5,6,7,8,11,11,12,13])

{2, 3, 4, 5, 6, 7, 8, 11, 12, 13}

and offcourse boolean

sure = True
arrr = False

print(sure, arrr)

True False

There is one very special object for nothing!

nothing = None

print(nothing)

None

nothing

a = {1,2}

a

{1, 2}

a = {[1,2,3], [1,2,3]}

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-132-5cdb72b857a9> in <module>()
----> 1 a = {[1,2,3], [1,2,3]}

TypeError: unhashable type: 'list'

Do it yourself¶

will this work?

pre = "Isac"
post = "Asimov"
name = pre post

What will be output of following sequence of command in interpreter, observe the special variable _
```
2 ** 2
_
a = 5 * 6
_
_ = 67
a/6 
_
31 // 6
```

Functions¶

Lets see some built in functions

len("Python")

6

len((1,2,3,4))

4

len([1,2,3,4,5,6,7])

7

len({"a":1})

1

len(set("Hello"))

4

4 + "2"

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-138-2957f6c14a52> in <module>()
----> 1 4 + "2"

TypeError: unsupported operand type(s) for +: 'int' and 'str'

str(4) + "2"

'42'

Problem : Using known functions find out number of digits in 2**100

len(str(2**100))

31

digits = str(2**100)

digits

'1267650600228229401496703205376'

len(digits)

31

Custom functions¶

def square(x):
    return x*x

def say_hello(name):
    print("Hello", name)

square(5)

25

say_hello("hari")

Hello hari

s = square(5)

s

25

r = say_hello("hari")

Hello hari

r

print(r)

None

say_hello(5)

Hello 5

print("Hello{}".format("hari"))

Hellohari

Do it youself¶

Write function count_digits to count number of digits in a given number.
```
count_digits(100)
3
```

def twice(x):
    return 2*x

def twice1(x):
    print(2*x)

twice(twice(3))

12

twice1(twice1(3))

6

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-157-c3f6229d2002> in <module>()
----> 1 twice1(twice1(3))

<ipython-input-155-3d4ed9845aa2> in twice1(x)
      3 
      4 def twice1(x):
----> 5     print(2*x)

TypeError: unsupported operand type(s) for *: 'int' and 'NoneType'

More about functions¶

Functions in python are nothing special as compared to other data types. but makes it very special

def func(x):
    return x*x

print(func)

<function func at 0x7f8f0c1b0488>

print([1,2,3])

[1, 2, 3]

type([1,2,3])

list

type(1)

int

type(func)

function

f = func

func(2)

4

f(2)

4

print(f)

<function func at 0x7f8f0c1b0488>

print(func)

<function func at 0x7f8f0c1b0488>

def summation(x,y):
    return x+y

def square(x):
    return x*x

def sumaofsquares(x, y):
    return square(x) + square(y)

def cube (x):
    return x**3

def sumofcubes(x,y):
    return cube(x) + cube(y)

def sumof(x, y, f):
    return f(x) + f(y)

sumaofsquares(2,3)

13

sumof(2, 3, square)

13

def cube (x):
    return x**3

def square(x):
    return x*x

def sumof(x, y, f):
    return f(x) + f(y)

sumof(2,3, cube)

35

sq = lambda x: x*x

sumof(2,3, sq)

13

def make_adder(y):
    return lambda x: x+y

add2 = make_adder(2)

print(add2)

<function make_adder.<locals>.<lambda> at 0x7f8f0c1b06a8>

add2(10)

12

There are some built in functions which take functions as argument

max(4,5)

5

max([1,2,3,4,5])

5

max(["one", "two", "three", "four", "five"])

'two'

words = ["one", "two", "three", "four", "five"]

max(words, key=len)

'three'

min(words, key=len)

'one'

We have record which contains scores of students stores as tuple in a list. We wish to find a student with max score.

scroresheet = [("vinay", 8.8, 14),
              ("vijay", 9.0, 14),
              ("vijaya", 9.9, 13),
              ("vishakha", 9.1, 12)]

def get_score(record):
    return record[1]

max(scroresheet, key=get_score)

('vijaya', 9.9, 13)

max(scroresheet)

('vishakha', 9.1, 12)

max(scroresheet, key= lambda r:r[1])

('vijaya', 9.9, 13)

Methods from objects¶

Objects of built in data type has some usefull functions as part of object. Those are called methods

string

book = "Alice in wonderland"

book.lower()

'alice in wonderland'

book.upper()

'ALICE IN WONDERLAND'

book.count('n')

3

book.split(" ")

['Alice', 'in', 'wonderland']

book.replace(" ","_")

'Alice_in_wonderland'

book.startswith("Alice")

True

book.endswith("alice")

False

lists

numbers = list(range(5,25,2))

numbers

[5, 7, 9, 11, 13, 15, 17, 19, 21, 23]

numbers.count(5)

1

numbers.count(" ")

0

numbers.reverse()

numbers

[23, 21, 19, 17, 15, 13, 11, 9, 7, 5]

numbers.append(0)

numbers

[23, 21, 19, 17, 15, 13, 11, 9, 7, 5, 0]

numbers.pop()

0

numbers

[23, 21, 19, 17, 15, 13, 11, 9, 7, 5]

numbers.sort(reverse=True)

numbers

[23, 21, 19, 17, 15, 13, 11, 9, 7, 5]

names = ['asawary', 'bahiravi','kalashri','tilak kamod']

names.sort()

names

['asawary', 'bahiravi', 'kalashri', 'tilak kamod']

names.sort(reverse=True,key=len)

names

['tilak kamod', 'bahiravi', 'kalashri', 'asawary']

names.extend(['yaman', 'malkauns'])

names

['tilak kamod', 'bahiravi', 'kalashri', 'asawary', 'yaman', 'malkauns']

tuple

numbers = (1,2,3,4)

numbers.count(1)

1

numbers.index(3)

2

DO it yourself¶

Write a function to count zeros in a given number
```
count_zeros(100)
2
```
Write a function head that takes list of words and returns first n words by dictionary order
```
head(['python','lisp', 'haskell', 'ocamel','ark', 'java'], 3)
['ark', 'haskell', 'java']
```

def count_zeros(n):
    return str(n).count('0')

def head(words, n):
    words.sort()
    return words[:n]

count_zeros(2**100)

6

head(['python','lisp', 'haskell', 'ocamel','ark', 'java'], 3)

['ark', 'haskell', 'java']

modules¶

For convinience related functions are organised inside a module. you can import these modules make use of functions or objects from that module

import math

def area_circle(radius):
    return math.pi * radius * radius

def polar_to_ractangular(radius, theta):
    return radius*math.cos(theta), radius*math.sin(theta)

area_circle(1)

3.141592653589793

polar_to_ractangular(1, math.pi/2)

(6.123233995736766e-17, 1.0)

x,y = polar_to_ractangular(1, 0)

x, y

(1.0, 0.0)

x, y = y , x

x, y

(0.0, 1.0)

import os

os.getcwd()

'/home/vikrant/trainings/2017/vmware-python'

os.getenv("PATH")

'/home/vikrant/usr/local/jupyter/bin:/home/vikrant/usr/local/jupyter/bin:/home/vikrant/bin:/home/vikrant/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games'

os.getlogin()

---------------------------------------------------------------------------
OSError                                   Traceback (most recent call last)
<ipython-input-252-64defab13146> in <module>()
----> 1 os.getlogin()

OSError: [Errno 25] Inappropriate ioctl for device

os.mkdir("/tmp/test1")

!ls /tmp/

config-err-0wn9Kp
firefox_vikrant
libgksu-2MwCiY
mintUpdate
ssh-J7HMapUgnss6
systemd-private-7e44d48da2304c6da1a992411d9711c9-colord.service-jaYyWy
systemd-private-7e44d48da2304c6da1a992411d9711c9-rtkit-daemon.service-E69o88
test1

os.listdir("/tmp/")

['libgksu-2MwCiY',
 '.XIM-unix',
 'ssh-J7HMapUgnss6',
 '.font-unix',
 'systemd-private-7e44d48da2304c6da1a992411d9711c9-rtkit-daemon.service-E69o88',
 'systemd-private-7e44d48da2304c6da1a992411d9711c9-colord.service-jaYyWy',
 'firefox_vikrant',
 '.ICE-unix',
 'config-err-0wn9Kp',
 '.X11-unix',
 'test1',
 '.X0-lock',
 '.Test-unix',
 'mintUpdate']

os.path.exists("/tmp/test1")

True

os.path.getsize("./Makefile")

617

Do it yourself¶

write a function countfiles to count number of files in a given directory
write a function biggestfile to find biggest file in a given directory

def biggestfile(directory):
    files = os.listdir(directory)
    return max(files, key=os.path.getsize)

biggestfile(os.getcwd())

'day1.html'

Custom modules¶

custom modules can be written by writing python statements and functions inside file with extension .py

%%file mymodule.py
import sys

def say_hello(name):
    print("Hello ", name)
    
print(sys.argv)

Writing mymodule.py

!python mymodule.py

['mymodule.py']

!python mymodule.py hello 1 2 3

['mymodule.py', 'hello', '1', '2', '3']

import mymodule

['/home/vikrant/usr/local/jupyter/lib/python3.5/site-packages/ipykernel_launcher.py', '-f', '/run/user/1000/jupyter/kernel-945e24ab-abf4-444f-a309-3861c167a644.json']

mymodule.say_hello("Python")

Hello  Python

help(mymodule)

Help on module mymodule:

NAME
    mymodule

FUNCTIONS
    say_hello(name)

FILE
    /home/vikrant/trainings/2017/vmware-python/mymodule.py

import random

random.choice(["python","lisp","haskell", "java"])

'python'

random.choice(["python","lisp","haskell", "java"])

'haskell'

senestence = "Pascal traingle is very simple structure but it has got very interesting properties"

random.choice(senestence.split())

'has'

Do it yourself¶

write a python script square.py that takes a number as commandline argument and prints square of that number
write a python script add.py that takes a two numbers as commandline arguments and prints addition of those numbers
write a python script echo.py which echoes whatever argument is given

%%file square.py
import sys

def square(x):
    return x*x

x = int(sys.argv[1])
value = square(x)
print(value)

Writing square.py

!python square.py 3

9

%%file echo.py
import sys

print(sys.argv[1:])

Writing echo.py

!python echo.py echoes this statement till end

['echoes', 'this', 'statement', 'till', 'end']

"_".join(["hello", "world", "make", "statement"])

'hello_world_make_statement'

%%file echo.py
import sys

print(" ".join(sys.argv[1:]))

Overwriting echo.py

!python echo.py echoes this statement till end

echoes this statement till end

there is special variable __name__

%%file anothermodule.py
print(__name__)

Writing anothermodule.py

!python anothermodule.py

__main__

import anothermodule

anothermodule

%%file echo.py
import sys

def echo():
    x = 0
    print(" ".join(sys.argv[1:]))
    
print(__name__)

if __name__ == "__main__":
    echo()

Overwriting echo.py

import echo

!python echo.py some commandline arguments

__main__
some commandline arguments