Python Virtual Training For Arcesium - Module I - Day 2

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-day2

Functions and Methods

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

5

len("hello")

5

d = {"one":1, "two":2}
len(d)

2

point = (0, 1, 2,3)
len(point)

4

max([3, 4, 5, 6])

6

min([3, 4, 5, 6])

3

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

11

x = input("Enter some value")

x # value taken as input is always text

'45'

int(x)

45

sorted([5, 6, 7, 2, 1, 4, 2, 4])

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

numbers = [34, 4 , 5, 6, 3, 2]

sorted(numbers)

[2, 3, 4, 5, 6, 34]

numbers

[34, 4, 5, 6, 3, 2]

string methods

textdata = "this is some text data"

textdata.startswith("this")

True

textdata.endswith("data")

True

textdata.endswith("Data")

False

textdata.islower() # are all character in this text in lower case?

True

x = input("Enter integer:")

x.isdecimal()

False

x.isdigit()

False

x.isalpha()

True

x.isalnum() # if text has alphabets or numbers

True

"variablename1232".isalnum()

True

textdata

'this is some text data'

textdata.upper()

'THIS IS SOME TEXT DATA'

textdata

'this is some text data'

textdata.capitalize() # make first char upper case

'This is some text data'

help(textdata.upper)

Help on built-in function upper:

upper() method of builtins.str instance
    Return a copy of the string converted to uppercase.

textdata.lower()

'this is some text data'

textdata.title()

'This Is Some Text Data'

textdata.center(50)

'              this is some text data              '

textdata.rjust(50)

'                            this is some text data'

textdata.ljust(50)

'this is some text data                            '

textdata.replace(" ", ",") # frequently used

'this,is,some,text,data'

textdata

'this is some text data'

text_with_commas = textdata.replace(" ", ",")

text_with_commas

'this,is,some,text,data'

textdata.split() # breaks the text data into smaller parts...break whereever there is empty space

['this', 'is', 'some', 'text', 'data']

"these,are,some,words,with,comma,in,between".split(",") # this will break data into smaller strings where ever there is comma

['these', 'are', 'some', 'words', 'with', 'comma', 'in', 'between']

paragraph = """this is data from
some imaginary novel
which I wil use for understanding 
split method of strings from python
language"""

words = paragraph.split()

len(words)

20

paragraph

'this is data from\nsome imaginary novel\nwhich I wil use for understanding \nsplit method of strings from python\nlanguage'

lines = paragraph.split("\n")

lines

['this is data from',
 'some imaginary novel',
 'which I wil use for understanding ',
 'split method of strings from python',
 'language']

len(lines)

5

page = """this is data from
some imaginary novel
which I wil use for understanding 
split method of strings from python
language

this is data from
some imaginary novel
which I wil use for understanding 
split method of strings from python
language

this is data from
some imaginary novel
which I wil use for understanding 
split method of strings from python
language
"""

page

'this is data from\nsome imaginary novel\nwhich I wil use for understanding \nsplit method of strings from python\nlanguage\n\nthis is data from\nsome imaginary novel\nwhich I wil use for understanding \nsplit method of strings from python\nlanguage\n\nthis is data from\nsome imaginary novel\nwhich I wil use for understanding \nsplit method of strings from python\nlanguage\n'

paras = page.split("\n\n")

len(paras)

3

words

['this',
 'is',
 'data',
 'from',
 'some',
 'imaginary',
 'novel',
 'which',
 'I',
 'wil',
 'use',
 'for',
 'understanding',
 'split',
 'method',
 'of',
 'strings',
 'from',
 'python',
 'language']

" ".join(words)

'this is data from some imaginary novel which I wil use for understanding split method of strings from python language'

",".join(words)

'this,is,data,from,some,imaginary,novel,which,I,wil,use,for,understanding,split,method,of,strings,from,python,language'

"_".join(words)

'this_is_data_from_some_imaginary_novel_which_I_wil_use_for_understanding_split_method_of_strings_from_python_language'

"-".join(words)

'this-is-data-from-some-imaginary-novel-which-I-wil-use-for-understanding-split-method-of-strings-from-python-language'

"/".join(words)

'this/is/data/from/some/imaginary/novel/which/I/wil/use/for/understanding/split/method/of/strings/from/python/language'

"/".join(["","home","vikrant","trainings","2021"])

'/home/vikrant/trainings/2021'

"\n"

'\n'

"\\"

'\\'

textdata.split()[-1]

'data'

textdata

'this is some text data'

textdata.replace("this", "that").replace("is","was")

'that was some text data'

problems

• There is a varaible name which is a senetence with words seperated by _. convert that name into normal text senetence i.e. words seperated by space

  name = "yet_another_variable_name_which_is_very_long"
  convert this to 
  yet another variable name which is very long

• On a website login , username can only be alphnumeric. user enter username in a variable username. how will you check if the name enetered follows the website's rule for username.

• A complete filepath is given for a file. Find out in which folder the file is.

filepath = "c:\\Program Files\\Python3.9.7\\bin\\python

filepath = "c:\\Documents\Welcome.docx"

• Using string methods , if filename is given as a string, can you find out extension of the file?

filename = "hello.xlsx"

"_".join("hello")# this is because join takes every item from "hello" andjoin it with _

'h_e_l_l_o'

"_".join(["test","this"])

'test_this'

"@232".isalnum()

False

"2323".isalnum()

True

"asa".isalpha()

True

"a123".isalnum()

True

"a123".isalpha() # this will check only aphabets

False

"\t" # this is not two char \ and t ... but it is single char \t

'\t'

len('\t')

1

"c:\Program Files\Python3.9.7\bin\python"

'c:\\Program Files\\Python3.9.7\x08in\\python'

print("c:\Program Files\Python3.9.7\nin\python")

c:\Program Files\Python3.9.7
in\python

r"c:\Program Files\Python3.9.7\bin\python" # r before " says that take this as raw string

'c:\\Program Files\\Python3.9.7\\bin\\python'

name = "yet_another_variable_name_which_is_very_long"
name.replace("_", " ")

'yet another variable name which is very long'

username = input("Eneter user name:")

username.isalnum()

True

filepath = "c:\\Program Files\\Python3.9.7\\bin\\python"

filepath.split("\\")[-2]

'bin'

filename = "hello.xlsx"

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

'xlsx'

filename = "hello.tar.gz"

filename.split(".")[-1] # text only after last . is taken as extension

'gz'

List methods

words = words[:8] # take first 8 words

words

['this', 'is', 'data', 'from', 'some', 'imaginary', 'novel', 'which']

words.index("is") # where is the location of 'is'

1

ones = [1, 1, 1, 1]

ones.index(1) # return location of first occurence of the item is present muliple times

0

words.count("some")

1

ones.count(1)

4

empty = []

empty.append(0)

empty

[0]

empty.append(1)

empty

[0, 1]

empty.append(3)

empty

[0, 1, 3]

words

['this', 'is', 'data', 'from', 'some', 'imaginary', 'novel', 'which']

words.insert(1, "extra") # this method modifies the list but does not return

words

['this', 'extra', 'is', 'data', 'from', 'some', 'imaginary', 'novel', 'which']

ones.extend([4, 4, 4])

ones

[1, 1, 1, 1, 4, 4, 4]

empty

[0, 1, 3]

empty.remove(3)

empty

[0, 1]

words

['this', 'extra', 'is', 'data', 'from', 'some', 'imaginary', 'novel', 'which']

words.remove('extra')

words

['this', 'is', 'data', 'from', 'some', 'imaginary', 'novel', 'which']

words.pop() # removes last item and also returns

'which'

words

['this', 'is', 'data', 'from', 'some', 'imaginary', 'novel']

words.sort()  # this modifies original list

words

['data', 'from', 'imaginary', 'is', 'novel', 'some', 'this']

numbers

[34, 4, 5, 6, 3, 2]

numbers.sort()

numbers

[2, 3, 4, 5, 6, 34]

numbers.reverse()

numbers

[34, 6, 5, 4, 3, 2]

Creating Custom Functions

def square(x):
    return x*x

def find_extension(filename):
    tokens = filename.split(".")
    return tokens[-1]


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

square

<function __main__.square(x)>

square(5)

25

square(10)

100

find_extension("hello.xlsx")

'xlsx'

def find_foldername(path, sep):
    tokens = path.split(sep)
    return tokens[-2]

find_foldername("c:\\Program Files\\Python3.9\\bin\\python.exe", "\\")

'bin'

find_extension("/home/vikrant/trainings/2021/arcesium_finop_bath2/index.html", "/")

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-143-00b2311d4da6> in <module>
----> 1 find_extension("/home/vikrant/trainings/2021/arcesium_finop_bath2/index.html", "/")

TypeError: find_extension() takes 1 positional argument but 2 were given

find_foldername("/home/vikrant/trainings/2021/arcesium_finop_bath2/index.html", "/")

'arcesium_finop_bath2'

find_foldername("/", "/home/vikrant/trainings/2021/arcesium_finop_bath2/index.html")

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-145-0ddeaebcc794> in <module>
----> 1 find_foldername("/", "/home/vikrant/trainings/2021/arcesium_finop_bath2/index.html")

<ipython-input-141-460699e2293c> in find_foldername(path, sep)
      1 def find_foldername(path, sep):
      2     tokens = path.split(sep)
----> 3     return tokens[-2]

IndexError: list index out of range

def find_foldername(path, sep):
    tokens = path.split(sep)
    return tokens[-2]

find_foldername(sep="/",path="/home/vikrant/trainings/2021/arcesium_finop_bath2/index.html")

'arcesium_finop_bath2'

def cylinder_volume(radius, height):
    return 3.14*radius**2*height

cylinder_volume(radius=1, height=2)

6.28

cylinder_volume(height=2, radius=1)

6.28

cylinder_volume(1, 2)

6.28

cylinder_volume(2, 1)# confusion! will get wrong results

12.56

square(5)

25

x = square(5)

x

25

def print_square(a):
    print(a*a)

print_square(5)

25

square(5)

25

m = square(5)

m

25

n = print_square(5)

25

print(n)

None

Any function that does not return a value by return statement , it returns None

Calling Function Vs Function

def add(2, 3): # incorrect
    return 2+3


def add("a", "b"): # incorrect
    return a + b

  File "<ipython-input-164-0010f66ae02c>", line 1
    def add(2, 3): # incorrect
            ^
SyntaxError: invalid syntax

def add(a, b): # this is correct and is just defination
    return a+b

add(2,3)

5

a = 5
b = 7
add(a, b) # a, b here are variables passed as argument

12

add(8, 10) # 8 and 10 here are literals

18

problems

• Net asset value or NAV is equls to fund's or company's total assets less its liabilities. NAV is usually calcaulated per share value for MF,ETF or closed ended fund. Write a function NAV which computes NAV. Compute NAV for total assets of 25,00,00,000 , liabilities 30,00,000 and 1000 shares

• In finiancial terms a negative balance is represented with round brackets around the number instead of - sign. Write a function numeric_value which returns actual numeric value. For example a value "(1234)" is passed as argument yu should get -1234.0 as a result. if "2345.5" is give as argument to function it should return 2345.5

• Have a look at following python code, what will it print, can you correct it if it wrong!

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


twice(twice(twice(5)))

def functionname(paramater1, prameter2)
return paramater1+paramater1

  File "<ipython-input-173-ad6a9b991906>", line 1
    def functionname(paramater1, prameter2)
                                           ^
SyntaxError: invalid syntax

def functionname(paramater1, prameter2):
return paramater1+paramater1

  File "<ipython-input-174-5345c3fafa0a>", line 2
    return paramater1+paramater1
    ^
IndentationError: expected an indented block

def functionname(paramater1, prameter2):
    return paramater1+paramater1

"hello".replace("hel", "cel")

'cello'

"hello".replace("cel", "del")

'hello'

#numeric_value("(1234)")
#-1234.0

float("(1243)")

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-179-985ba27261d0> in <module>
----> 1 float("(1243)")

ValueError: could not convert string to float: '(1243)'

def numeric_value(strnum):
    corrected_num = strnum.replace("(", "-").replace(")","")
    return float(corrected_num)

numeric_value("(34343)")

-34343.0

numeric_value("543543")

543543.0

"(test)".remove(")")

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-183-c96c8ee5bd88> in <module>
----> 1 "(test)".remove(")")

AttributeError: 'str' object has no attribute 'remove'

"(test)".replace(")","")

'(test'

def numericvalue(accvalue):
    accvalue.replace("(", "-") # replaced dat is not stored anywhere
    accvalue.replace(")","")
    return float(accvalue)

text = "testdata"

text.replace("test","this")

'thisdata'

text

'testdata'

x = text.replace("test","this")

x

'thisdata'

text = text.replace("test","this")

text

'thisdata'

def numericvalue(accvalue):
    local_var = accvalue.replace("(", "-") # replaced dat is not stored anywhere
    xyz = local_var.replace(")","")
    return float(xyz)

numericvalue("(23232)")

-23232.0

• Have a look at following python code, what will it print, can you correct it if it wrong!

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


twice(twice(twice(5)))