Python Virtual Training For Arcesium - Module I - Day 4

Sep 20-24, 2021 Vikrant Patil

These notes are available online at https://notes.pipal.in/2021/arcesium_finop_batch2/

© Pipal Academy LLP

Day 1 | Day 2 | Day 3 | Day 4 | Day 5

We will be using jupyter hub from https://lab2.pipal.in for this training.

login to hub and create a notebook with name module1-day4

Conditions

"text".isalpha()

True

"hel" in "hello"

True

text = "Hello this is some text"

"this" in text

True

"that" in text

False

x = "is"

x in text

True

1 in [1, 1, 1, 12, 3]

True

1 in [0, 0, 3, 4]

False

1 in [(1, 0, 1),(1, 0),(0, 0)]

False

1 in (1, 0, 1)

True

1 in [[1, 1], [2, 1]]

False

[1, 1] in [[1,1], [2,1]]

True

person = {"name":"Vikrant", "language":"Marathi", "country":"India"}

person

{'name': 'Vikrant', 'language': 'Marathi', 'country': 'India'}

"name" in person # you can check if the left hand side is part of keys

True

"Vikrant" in person

False

"Vikrant" in person.values() # method from dictionary 

True

"name" not in text

True

x, y = 5, 6

x == y

False

"text" == "text"

True

x < y

True

y <= y

True

x != y

True

cell = "cell"
hell = "hell"
bell = "bell"

if "hel" in cell: # the if line has to end with :
    print("We are in hell!") # next line/lines should be indented by 4 spaces
elif "cel" in hell: # optional
    print("We are in a cell!")
elif "del" in bell: # optional but you can start with this
    print("Delete!")
else: # optional but you can start with this
    print("Finally ..we are out from if else...")

Finally ..we are out from if else...

x = 2 if "hel" in hell else 3 # if very simple conditions and simple assignemt ..this one liner can be used

x

2

While Loop

numbers = [45, 231, 11, 44, 1, 678, 43]

numbers[0]

45

i = 4
numbers[i]

1

i = 0
n = len(numbers)
while i < n:
    print(numbers[i])
    i = i + 1  
    # i += 1

45
231
11
44
1
678
43

def print_list(items):
    i = 0
    size = len(items)
    while i < size: # source of bug or infinite loop!
        print(items[i], end=",")
        i += 1 # if you forget to change i .. 

words = "if very simple conditions and simple assignemt ..this one liner can be used".split()

words

['if',
 'very',
 'simple',
 'conditions',
 'and',
 'simple',
 'assignemt',
 '..this',
 'one',
 'liner',
 'can',
 'be',
 'used']

print_list(words)

if,very,simple,conditions,and,simple,assignemt,..this,one,liner,can,be,used,

print_list(numbers)

45,231,11,44,1,678,43,

print_list("some text data")

s,o,m,e, ,t,e,x,t, ,d,a,t,a,

print_list((1,2,4,3,4,54,4))

1,2,4,3,4,54,4,

### fibn = fibn-1 + fibn-2

def print_fib(n):
    """
    print fibonacci numbers less than n
    """
    
    curr, prev = 1, 1
    
    while prev < n:
        print(prev, end=",")
        curr, prev = curr + prev, curr

print_fib(100)

1,1,2,3,5,8,13,21,34,55,89,

def print_list1(items):
    i = 0
    size = len(items)
    while i < size: # source of bug or infinite loop!
        print(items[i], end=",")
    i += 1 # this statement is outside loop! this will result in infinite loop! 
    

For loop

words

['if',
 'very',
 'simple',
 'conditions',
 'and',
 'simple',
 'assignemt',
 '..this',
 'one',
 'liner',
 'can',
 'be',
 'used']

students = ["Akash", "Aksh", "Akanksha", "Arjun"]

for word in words:
    print(word, end=",")

if,very,simple,conditions,and,simple,assignemt,..this,one,liner,can,be,used,

for char in "text is fun":
    print(char, end=",")

t,e,x,t, ,i,s, ,f,u,n,

for w in words:
    print(w, end=",")

if,very,simple,conditions,and,simple,assignemt,..this,one,liner,can,be,used,

for student in students:
    print(student.upper(), end=" ")

AKASH AKSH AKANKSHA ARJUN 

for s in students:
    print(s)

Akash
Aksh
Akanksha
Arjun

for loop can be applied to any coolection i.e. list, tuple, string, dictionary , set

point = (3, 4, 5)
for coordinate in point:
    print(coordinate)

3
4
5

text = "hello this is text"
for c in text:
    print(c, end="-")

h-e-l-l-o- -t-h-i-s- -i-s- -t-e-x-t-

person

{'name': 'Vikrant', 'language': 'Marathi', 'country': 'India'}

for key in person:
    print(key)

name
language
country

for key in person:
    print(key, person[key])

name Vikrant
language Marathi
country India

def mysum(numbers):
    s = 0 
    for n in numbers:
        s += n
    
    return s

mysum(numbers)

1053

def mysum_(numbers):
    s = 0 
    for n in numbers:
        s += n
    
        return s # this will return after first iteration

numbers

[45, 231, 11, 44, 1, 678, 43]

mysum_(numbers)

45

def uppercase(text_items):
    """converts every text item from text_items to upper case
    and returns a new list
    """
    caps_data = [] # start with empty list
    
    for text in text_items:
        caps_data.append(text.upper())
        
    return caps_data

uppercase(words)

['IF',
 'VERY',
 'SIMPLE',
 'CONDITIONS',
 'AND',
 'SIMPLE',
 'ASSIGNEMT',
 '..THIS',
 'ONE',
 'LINER',
 'CAN',
 'BE',
 'USED']

lines = """first line
second line
third line
fourth line
fifth line
""".split("\n")

lines

['first line', 'second line', 'third line', 'fourth line', 'fifth line', '']

uppercase(lines)

['FIRST LINE', 'SECOND LINE', 'THIRD LINE', 'FOURTH LINE', 'FIFTH LINE', '']

problem

• Write a function product which finds product of all items form a list.

  >>> product([3, 2, 4])
  24

• Write a function factorial to find factorial of a number. can you make use of range and product that we wrote in problem above

  >>> factorial(5)
  120

• Write a function findlens which finds length of every item from given collection

  >>> findlens(["one", "two", "three"])
  [3, 3, 5]

• Write a function find_words_of_len to find words of given length from given collection.

  >>> words = ["one", "two", "three"]
  >>> find_words_of_len(words, 3)
  ["one", "two"]

for i in range(5): # gives me numbers from 0 to 4
    print(i)

0
1
2
3
4

for i in range(1, 11): #gives integers from 1 to 10
    print(i, end=" ")

1 2 3 4 5 6 7 8 9 10 

for i in range(1, 20, 3): # gives integers starting from 1 , less than 20 and every 3rd item
    print(i, end=",")

1,4,7,10,13,16,19,

for word in words: # there is no need of any indexing!
    print(word)

if
very
simple
conditions
and
simple
assignemt
..this
one
liner
can
be
used

When to use for loop

• When we want to access items from list, tuple, string, dictionary, set, range
• if there is no collection at hand but we want to work on loop with integers then make use use of range and for

When to use while loop

• when there is no collection on which we can put a for loop
• there is only condition

Medium level Problems

• Write a function unique which will remove duplicate entries from a list

  >>> unique([1, 1, 2, 3, 1, 2, 3, 4, 3])
  [1, 2, 3, 4]

• List of urls is given as a list. Some urls are from same domain and some are from different domain. Find unique domain names used in all of these urls

  urls = ["www.abrakadabra.com/dsjhj/sdhhHHG",
  "www.abrakadabra.com/jkj/dfkdjgkj",
  "www.abra.com/lkji/uywe",
  "www.dabra.com/oiuytw/feowu",
  "www.abrakadabra.com/Asldk/kjhkKJH",
  "www.abra.com/jhkjh/iuroiwue",
  "www.dabra.com/yYIU/UYUY",
  "www.abra.com/JHKJH",
  "www.dabra.com/HJHJH,
  "www.abra.com/ABCD"]

• Write a function min2 which find minium from given two numbers. Also write a function min3 which find minimum from 3 numbers. DO not make use of builf min function.
• Write a function which will check if given number if palindrome or not!

len

<function len(obj, /)>

len(words)

13

len = []

len

[]

len(words)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-74-a5004d9b095c> in <module>
----> 1 len(words)

TypeError: 'list' object is not callable

del len

len(words)

13

def find_words_of_len(itemlist, l):
    lens = findlens(itemslist)
    i = 0
    for length in lens:
        if lenght == l:
            print(itemlist[i])
        i += 1

def find_words_of_len(itemlist, l):
    for item in itemlist:
        if len(item) == l:
            print(item)

def find_words_of_len(itemlist, l):
    words = []
    for item in itemlist:
        if len(item) == l:
            words.append(item)

def product(numbers):
    """find product of all numbers from a collection!
    """
    p = 1
    
    for n in numbers:
        p = p*n
        
    return p

product(numbers)

146679021720

numbers

[45, 231, 11, 44, 1, 678, 43]

def factorial(n):
    """n! = n*(n-1)*(n-2)*(n-3).....1
    range(1, n+1) -> 1, 2, 3, 4, 5...
    """
    return product(range(1, n+1))

factorial(5)

120

factorial(10)

3628800

def findlens(items):
    lengths = []
    
    for item in items:
        lengths.append(len(item))
        
    return lengths

findlens(words)

[2, 4, 6, 10, 3, 6, 9, 6, 3, 5, 3, 2, 4]

words

['if',
 'very',
 'simple',
 'conditions',
 'and',
 'simple',
 'assignemt',
 '..this',
 'one',
 'liner',
 'can',
 'be',
 'used']

def find_words_of_len(items, l):
    
    words_of_len = []
    
    for item in items:
        if len(item)==l:
            words_of_len.append(item)
    
    return words_of_len

find_words_of_len(words, 3)

['and', 'one', 'can']

find_words_of_len(words, 5)

['liner']

4 in [1, 2, 3]

False

4 in [1, 2, 3, 4]

True

def unique(items):
    seen = []
    
    for item in items:
        if item not in seen:
            seen.append(item)
            
    return seen

unique([1, 1, 1, 2, 2, 3, 3, 4, 1, 2, 1])

[1, 2, 3, 4]

1, 1, 1, 2, 2, 3, 3, 4, 1, 2, 1
^
unique => 

def unique(inputlist):
    mycollection = []

    for item inputlist:
        if item not in mycollction:
           mycollection.append(item)

urls = ["www.abrakadabra.com/dsjhj/sdhhHHG",
    "www.abrakadabra.com/jkj/dfkdjgkj",
    "www.abra.com/lkji/uywe",
    "www.dabra.com/oiuytw/feowu",
    "www.abrakadabra.com/Asldk/kjhkKJH",
    "www.abra.com/jhkjh/iuroiwue",
    "www.dabra.com/yYIU/UYUY",
    "www.abra.com/JHKJH",
    "www.dabra.com/HJHJH",
    "www.abra.com/ABCD"]

urls[0].split("/")[0]

'www.abrakadabra.com'

def domain(url):
    return url.split("/")[0]


def all_domains(urls):
    domains = []
    
    for url in urls:
        domains.append(domain(url))
    
    return domains


def unique_domains(urls):
    domains = all_domains(urls)
    return unique(domains)
    

unique_domains(urls)

['www.abrakadabra.com', 'www.abra.com', 'www.dabra.com']

x = 2==3

x

False

3 4 1 6 7 2 4 2 1 8 -3 .....

m    next number
3     -
3     4
1     1
1     6
...


-3

def min2(x, y):
    if x < y:
        return x
    else:
        return y
    
    
def min3(x, y, z):
    if x < y and x < z:
        return x
    elif y < x and y < z:
        return y
    else:
        return z
    
    
def min3(x, y, z):
    return min2(min2(x, y), z)


def min3(x, y, z):
    m = min2(x, y)
    return min2(m , z)

"madam"

'madam'

"12321"

'12321'

word = "hello"

#word == reverse_word(word)

word[:2] # take first 2 items

'he'

word[2:] # drom first two items

'llo'

word[::] # copy

'hello'

word[::-1] # reverse

'olleh'

def is_palindrom(item):
    stritem = str(item)
    return stritem == stritem[::-1]

is_palindrom("madam")

True

is_palindrom(121)

True

is_palindrom(123)

False

Modules

import os # will import built in os module

os.getcwd() # this function returns current working directory/folder

'/home/vikrant/trainings/2021/arcesium_finop_batch2'

os.listdir() # this function retuns listing from current directory/folder

['index.html',
 'push',
 'Untitled.html',
 'index.ipynb',
 'module1-day1.html',
 'module1-day1.ipynb',
 'module1-day2.ipynb',
 'module1-day3.html',
 'module1-day2.html',
 'module1-day3.ipynb',
 'module1-day4.html',
 'Makefile',
 '.ipynb_checkpoints',
 'module1-day4.ipynb']

os.listdir("/etc/ssh/") # if you pass path here , it will give listing from that directory

['ssh_host_ed25519_key',
 'ssh_host_rsa_key.pub',
 'ssh_host_ecdsa_key.pub',
 'ssh_config.d',
 'ssh_host_ecdsa_key',
 'sshd_config',
 'ssh_host_ed25519_key.pub',
 'ssh_host_rsa_key',
 'ssh_import_id',
 'moduli',
 'ssh_config',
 'sshd_config.d']

os.path # this submodule inside os

<module 'posixpath' from '/home/vikrant/anaconda3/lib/python3.8/posixpath.py'>

os.path.isfile("index.html")

True

os.path.isfile(".ipynb_checkpoints")

False

os.path.isdir(".ipynb_checkpoints")

True

os.path.isdir("module1-day1.ipynb")

False

os.path.isfile("module1-day1.ipynb") # relative path, with respect current directory

True

os.path.isfile("/etc/ssh/") # this called as absolute path c:\\Program File\\Python\\

False

if you want to do any of these checks on files and folders which are not in current directory, then you will have to give absolute path (which means it should start from the drive)

os.path.exists("imaginary.txt")

False

os.path.isfile("imaginary.txt") # i might think that this is probabality a directory

False

listings = os.listdir() #this does not go recursively

for file in listings:
    print(os.path.exists(file))

True
True
True
True
True
True
True
True
True
True
True
True
True
True

os.path.getsize("module1-day4.ipynb") # gives size of file in bytes

48792

import os

from os import getcwd # this will import the function

getcwd()

'/home/vikrant/trainings/2021/arcesium_finop_batch2'

import os as operatingsystem

import math as m

m.sin(6.3)

0.016813900484349713

os.path.getsize("profile")

---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
<ipython-input-158-c279218e8543> in <module>
----> 1 os.path.getsize("profile")

~/anaconda3/lib/python3.8/genericpath.py in getsize(filename)
     48 def getsize(filename):
     49     """Return the size of a file, reported by os.stat()."""
---> 50     return os.stat(filename).st_size
     51 
     52 

FileNotFoundError: [Errno 2] No such file or directory: 'profile'