Python Virtual Training For Arcesium - Module I - Day 2

Sep 13-17, 2021 Vikrant Patil

These notes are available online at https://notes.pipal.in/2021/arcesium_finop_batch1/module1-day2.html

© Pipal Academy LLP

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

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

login to hub and create a notebook with name module1-day2

Functions

built in functions

name = "rupali"

len(name)

6

numbers = [1, 2, 3, 4, 5, 6]

len(numbers) # with tab you can auto-complete the variable name, function names or build ins

6

len(numbers)

6

point = (0, 0, 0)

len(point)

3

stock = {"name":"IBM", "open":124, "close":125}

len(stock)

3

type conversion

p = input("Enter value of principle amount:")

p

'20000'

p + 200

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-13-3698dda22622> in <module>
----> 1 p + 200

TypeError: can only concatenate str (not "int") to str

len(p)

5

p**2

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-15-ab546129d7fc> in <module>
----> 1 p**2

TypeError: unsupported operand type(s) for ** or pow(): 'str' and 'int'

int(p)

20000

p

'20000'

principle = int(p)

principle + 200

20200

principle**0.05

1.6407843301899723

float("20.5")

20.5

float(5)

5.0

str(principle)

'20000'

list("hello")

['h', 'e', 'l', 'l', 'o']

some_numbers = input("Enter list of numbers:")

some_numbers

'[1, 2, 3, 4, 5]'

some_numbers[0]

'['

some_numbers[-1]

']'

list(some_numbers)

['[', '1', ',', ' ', '2', ',', ' ', '3', ',', ' ', '4', ',', ' ', '5', ']']

stock

{'name': 'IBM', 'open': 124, 'close': 125}

list(stock) # works only on collections , where it creates a list from items in given

['name', 'open', 'close']

list(point)

[0, 0, 0]

point

(0, 0, 0)

max([42, 45, 343, 67, 34])

343

min(numbers)

1

sum(numbers)

21

sum(["a","b","c"])

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-37-839ac8434816> in <module>
----> 1 sum(["a","b","c"])

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

"a" + "b"

'ab'

problem

• Use python to find total income if the person has four sources of incomes 32344, 435454, 5454, 43545
• Find how many digits are there in 2 raised to power 100
• Use python to find highest income from example 1.5

incomes = [32344, 435454, 5454, 43545]
total_income = sum(incomes)

print(total_income)

516797

max_income = max(incomes)

x = 10
y = x
x = 30

max = max(incomes) # by mistake overwrote python function! variable name should be from built in functions

max

435454

max(incomes)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-45-9070a17d57e1> in <module>
----> 1 max(incomes)

TypeError: 'int' object is not callable

del max

max_ = max(incomes)

max_

435454

max_income = max(incomes)

2**100

1267650600228229401496703205376

power_2_100 = 2**100

print(power_2_100)

1267650600228229401496703205376

len(power_2_100)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-56-c26ee8a0acd7> in <module>
----> 1 len(power_2_100)

TypeError: object of type 'int' has no len()

len(str(power_2_100)) # nested calling!

31

digits_text = str(power_2_100)
len(digits_text)

31

2^100 # this is bitwise operator

102

max(3, 5, 6)

6

sum(2, 3, 4)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-62-fc2d57a9194a> in <module>
----> 1 sum(2, 3, 4)

TypeError: sum() takes at most 2 arguments (3 given)

help(sum)

Help on built-in function sum in module builtins:

sum(iterable, /, start=0)
    Return the sum of a 'start' value (default: 0) plus an iterable of numbers
    
    When the iterable is empty, return the start value.
    This function is intended specifically for use with numeric values and may
    reject non-numeric types.

help(max)

Help on built-in function max in module builtins:

max(...)
    max(iterable, *[, default=obj, key=func]) -> value
    max(arg1, arg2, *args, *[, key=func]) -> value
    
    With a single iterable argument, return its biggest item. The
    default keyword-only argument specifies an object to return if
    the provided iterable is empty.
    With two or more arguments, return the largest argument.

p = {1, 2, 2, 3} # this set, it makes a  unique collection

p

{1, 2, 3}

len(p)

3

incomes = {"shares": 50000, "salary":300000, "rent":100000}

max(incomes) # this will order the keys in dictionary order and give me last item

'shares'

len(incomes)

3

list(incomes)

['shares', 'salary', 'rent']

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

'two'

[3, 878, 2, 1, 7]-> [1, 2, 3, 7, 878]
["a", "ab", "abc", "b", "boo", "bool"] # dictionary order

max(["one", "two", "three"], key=len)

'three'

list slicing

numbers

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

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

digits[2:8:2] # give me items from position 2 till 8 (exludes this) , every second item

[2, 4, 6]

list[start:end:step]

digits[2:8] # all items from index 2 till index 8 (exluding)

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

digits[:5] # take first five items

[0, 1, 2, 3, 4]

digits[5:] # drop first five items

[5, 6, 7, 8, 9]

digits[:] # take all..copy

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

digits[::-1] # reverse order

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

• if step is not given it is taken as 1
• if start is not given it is taken as initial
• if end is not given it is taken as lat position in the list

Methods

len(numbers) # function

6

digits

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

len(digits)

10

sorted(digits)

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

sorted(digits, reverse=True)

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

digits

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

digits[0] = -1

digits

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

sentence = "These are some wise words"

sentence.startswith("This")

False

sentence.startswith("These")

True

sentence.endswith("false")

False

sentence.endswith("words") # argument to this method is litteral string

True

sentence = input("enter your statement")
word = input("enter the word whose existence you want check at end of statement")
print(sentence.endswith(word))

True

2 + 3
5+6
2**15
4*5 

20

print(2 + 3)
print(5+6)
print(2**15)
print(4*5) 

5
11
32768
20

sentence.isupper()

False

"HELLO".isupper()

True

sentence.istitle()

False

sentence.isalnum()

False

sentence.isprintable()

True

"\n".isprintable()

False

sentence.upper()

'HELLO THIS IS THIRD TIME!'

sentence

'hello this is third time!'

sentence.upper()

'HELLO THIS IS THIRD TIME!'

sentence.capitalize()

'Hello this is third time!'

sentence.title()

'Hello This Is Third Time!'

sentence.center(50)

'            hello this is third time!             '

sentence.rjust(50)

'                         hello this is third time!'

sentence.ljust(50)

'hello this is third time!                         '

sentence.replace("third", "quite a many")

'hello this is quite a many time!'

print(sentence.replace("third", "quite a many")) # this will print only items from the string..

hello this is quite a many time!

"hello 234".isalnum()

False

"khfkjdshf".isalnum()

True

"dfhkjdshfkjs123".isalnum()

True

"fdshf 76786dsad".isalnum() # this text does have at least one char which is neither alphabet not a numeric digit

False

" ".isspace()

True

"    \n      \t".isspace()

True

" " in sentence # this checkes whether " " is there in sentence

True

sentence

'hello this is third time!'

sentence.split() # split the sentence using whitespace (space, \t \n)

['hello', 'this', 'is', 'third', 'time!']

path = "c:\\Program Files\\Python"
path.split("\\") 

['c:', 'Program Files', 'Python']

path = r"c:\Program Files\Python" # raw string
sep = "\\"
path.split(sep)

['c:', 'Program Files', 'Python']

"commas,are,there,between,these,words".split(",")

['commas', 'are', 'there', 'between', 'these', 'words']

words = ['commas', 'are', 'there', 'between', 'these', 'words']

words

['commas', 'are', 'there', 'between', 'these', 'words']

",".join(words)

'commas,are,there,between,these,words'

" ".join(words)

'commas are there between these words'

folders = ["/","home","vikrant","training","arcesium"]
"/".join(folders)

'//home/vikrant/training/arcesium'

problem

• Using string methods find extension of the filename. filename is stored in a variable `filename="hello.xlsx"

filename="hello.xlsx"

filename.split(".")

['hello', 'xlsx']

filename.split(".")[-1]

'xlsx'

List methods

numbers

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

numbers.index(3) # what is the location of this value , 3

2

[1, 2, 3, 4, 5, 6]
 0  1  2  3  4  5   <---- index

['a', 'b', 'c', 'd']
  0    1    2    3

nums = [1, 2, 4, 2, 3, 4] # what is the item comes many times in the list?

nums.index(2) 

1

nums.count(2)

2

nums.count(3)

1

items = ['a', 'b', 'c', 'd']

items.index("a")

0

items.index("b")

1

empty = []

empty.append(1) ## adds item at last

empty.append(3)

empty

[1, 3]

empty.append(4)

empty  # there will be two 4s because I executed above statement twice in my interpreter

[1, 3, 4, 4]

value = 24
loc = 2
empty.insert(loc, value) # note that assignment is not needed 

empty

[1, 3, 24, 4, 4]

numbers = (1, 2, 3, 4)

list(numbers)

[1, 2, 3, 4]

numbers

(1, 2, 3, 4)

numbers = list(numbers)

numbers

[1, 2, 3, 4]

numbers.extend([2,3,4]) # again no assignment needed

numbers

[1, 2, 3, 4, 2, 3, 4]

items

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

items.remove('a') # no assignment required, list is modified directly

items

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

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

items.remove('a') # will remov whatever occurs first

items =  ['a','b','c','d']
items.pop()
print(items)

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

items =  ['a','b','c','d']
last = items.pop()
print("items after pop" , items)
print("popped item", last)

items after pop ['a', 'b', 'c']
popped item d

item

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

items =  ['a','b','c','d']
second = items.pop(2)
print("items after pop" , items)
print("popped item", second)

items after pop ['a', 'b', 'd']
popped item c

numbers

[1, 2, 3, 4, 2, 3, 4]

numbers.sort() #it sorts in place

numbers

[1, 2, 2, 3, 3, 4, 4]

numbers.reverse() # will reverse the lisy in place!

Functions

def square(x):
    sqr = x*x
    return sqr

square(34)

1156

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

add(3, 4)

7

def sum_2(a, b):
    return a+b

def sumofsquares(a, b):
    return square(a) + square(b)

sumofsquares(3, 4)

25

v = 2

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-207-047e21bebf5f> in <module>
----> 1 v.to_bytes()

TypeError: to_bytes() missing required argument 'length' (pos 1)