Module I - Day 4

Python Foundation

Nov-Jan 2025 batch, Vikrant Patil

Date: 26 Nov 2025

loops

when we want to repeat some part of code
we want to some thing again and again till some condition is valid
we want to do something on every item from a collection

nums = [1, 2, 3, 5, 7, 11, 13]

for every_object in collection:
    do_some_operation(every_object)

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
Cell In[2], line 1
----> 1 for every_object in collection:
      2     do_some_operation(every_object)

NameError: name 'collection' is not defined

for n in nums:
    print(n)

for n in nums:
    print(n*n)

one major iteration pattern using for loop is to create a new collection using existing collection

nums -> squares of nums
nums -> absolute value of all numbers
words -> a new list of words where every word is uppper case

sqrs = []
for n in nums:
    sqr = n*n
    sqrs.append(sqr)

sqrs

[1, 4, 9, 25, 49, 121, 169]

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

caps_words= []
for w in words: # w is called as iteration variable .. it takes values from the collection one by one
    caps_words.append(w.upper())
print(caps_words) # look at the indentation. it means for loop is over

['ONE', 'TWO', 'THREE', 'FOUR', 'FIVE']

caps_words= []
for w in words: # w is called as iteration variable .. it takes values from the collection one by one
    caps_words.append(w.upper())
    print(caps_words) # look at the indentation. it means it is part of loop

['ONE']
['ONE', 'TWO']
['ONE', 'TWO', 'THREE']
['ONE', 'TWO', 'THREE', 'FOUR']
['ONE', 'TWO', 'THREE', 'FOUR', 'FIVE']

def fiboncci(n):
    if n<= 1:
        return 1
    else:
        return fiboncci(n-1) + fiboncci(n-2)

fiboncci(10)

for loop works on collection. - what if I want to put a loop that runs n times but I do not have collection - there is a way to create a dummy collection called range

range(10) # this will create numbers from 0 to 9

range(0, 10)

for i in range(10):
    print(i, end=",")

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

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

1 2 3 4 5 6 7 8 9 10

problem - make use of fibonacci function to create a list that has first 10 fibonacci numbers.

[one, two, three, four, five]

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
Cell In[18], line 1
----> 1 [one, two, three, four, five]

NameError: name 'one' is not defined

one is taken as variable name

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

['one', 'two', 'three', 'four', 'five']

words=["one","two","tree","four"]
caps_words=[]
for w in words:
    caps_words=caps_words.append(w.upper())

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Cell In[20], line 4
      2 caps_words=[]
      3 for w in words:
----> 4     caps_words=caps_words.append(w.upper())

AttributeError: 'NoneType' object has no attribute 'append'

ones = [1, 1, 1]

ones.append(2) # there is response by interpreter! but it has appended

ones

[1, 1, 1, 2]

def foo():
    pass

def bar():
    return 1

foo()

bar()

x = foo()

y = bar()

print(x, y)

None 1

return_value = ones.append(2)

print(return_value)

None

words=["one","two","tree","four"]
caps_words=[]
for w in words:
    caps_words.append(w.upper())

caps_words

['ONE', 'TWO', 'TREE', 'FOUR']

make use of fibonacci function to create a list that has first 10 fibonacci numbers.

first 10 natural number - range(1, 11)
for i in range(1, 11): fibonacci(i)

bonus problem - Write a function product which will find product of numbers from given list

>>> product([1, 2, 3, 4])
24

sum([1, 2, 3, 4, 5, 7, 23])

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

1, 2, 3, 4, 5, 6
0 + 1 =>1
1 + 2 => 3
3 + 3 => 6
6 + 4 => 10
10 + 5 => 15
15 + 6 => 21

mysum([1, 2, 3, 4, 5, 6])

problem - write a function to compute factorial which computes factorial of given n

>>> factorial(5)
120

def product(numbers):
    p = 1
    for n in numbers:
        p = p * n
    return p

five = [1, 2, 3, 4, 5]
product(five)

six = [1, 2, 3, 4, 5, 6]
product(six)

def factorial(n):
    return product(range(1, n+1))

factorial(10)

factorial(5)

modules

random

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
Cell In[43], line 1
----> 1 random

NameError: name 'random' is not defined

import random

random

<module 'random' from '/usr/lib/python3.13/random.py'>

random.random()  # this is function which generates random number between 0 to 1

0.19248968668834499

random.choice(nums) # choose random item from given collection

import math

math.pi

3.141592653589793

math.e

2.718281828459045

math.sin(math.pi)

1.2246467991473532e-16

5**3

math.pow(5, 3)

125.0

import os

os.getcwd() # get current working directory/folder

'/home/vikrant/programming/work/github/vikrant.dev/python-foundation-professionals'

os.getenv("HOME") # gives environment variable

'/home/vikrant'

os.listdir("/home/vikrant/trainings/")

['2023',
 '2018',
 'nakul',
 'day5.org',
 '2022',
 'hello.py',
 'day5.org~',
 '2024',
 'selenium_code_for_team',
 '2020',
 'trainingvenv',
 '2021',
 '2019',
 '2025',
 '2017',
 'indexdata.xlsx',
 'selenium_venv']

os.listdir() # by default it will return files/folders from current working directory

['index.qmd',
 'topics.qmd~',
 'notes.qmd',
 '_quarto.yml',
 'notes.qmd~',
 'day4.org~',
 'push',
 'styles.css',
 'trainer.qmd',
 '.quarto',
 'index.qmd~',
 'day4.org',
 '_quarto.yml~',
 '_site',
 '.gitignore',
 'module1-day1.ipynb',
 'module1-day2.ipynb',
 'topics.qmd',
 'about.qmd',
 'module1-day3.ipynb',
 'Makefile~',
 'Makefile',
 '.ipynb_checkpoints',
 'module1-day4.ipynb']

os.path # is submodule in os module

<module 'posixpath' (frozen)>

os.path.isdir("/home/vikrant/trainings/")

True

os.path.isdir("/home/vikrant/trainings/day5.org")

False

os.path.isfile("/home/vikrant/trainings/day5.org")

True

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

files = os.listdir()

files

['index.qmd',
 'topics.qmd~',
 'notes.qmd',
 '_quarto.yml',
 'notes.qmd~',
 'day4.org~',
 'push',
 'styles.css',
 'trainer.qmd',
 '.quarto',
 'index.qmd~',
 'day4.org',
 '_quarto.yml~',
 '_site',
 '.gitignore',
 'module1-day1.ipynb',
 'module1-day2.ipynb',
 'topics.qmd',
 'about.qmd',
 'module1-day3.ipynb',
 'Makefile~',
 'Makefile',
 '.ipynb_checkpoints',
 'module1-day4.ipynb']

for f in files:
    print(f, os.path.getsize(f))

index.qmd 677
topics.qmd~ 1043
notes.qmd 229
_quarto.yml 565
notes.qmd~ 200
day4.org~ 54
push 0
styles.css 17
trainer.qmd 1193
.quarto 4096
index.qmd~ 141
day4.org 84
_quarto.yml~ 525
_site 4096
.gitignore 29
module1-day1.ipynb 50000
module1-day2.ipynb 56885
topics.qmd 897
about.qmd 40
module1-day3.ipynb 50772
Makefile~ 586
Makefile 659
.ipynb_checkpoints 4096
module1-day4.ipynb 27846

max(files) # by dictionary order

'trainer.qmd'

max(files, key=os.path.getsize)

'module1-day2.ipynb'

import math

import math as m # here m becomes the math module

m.pi

3.141592653589793

from math import sin

sin(3.14/2)

0.9999996829318346

problem

Write a function longlistdir which will print filenames and folder names in a given folder, such that before every folder it prints a charecter d, and before every file it prints f.

    >>> longlistdir("/home/vikrant/training")
    d arcesium_batch1_module1
    f notes.txt
    f hello.py
    f scratch.ipynb

def print_parity(numbers):
    for n in numbers:
        if n%2 == 0:
            print("even", n)
        else:
            print("odd", n)

print_parity(nums)

odd 1
even 2
odd 3
odd 5
odd 7
odd 11
odd 13

def print_file_dir(files):
    for filename in files:
        if os.path.isfile(filename):
            print("f", filename)
        else:
            print("d", filename)

files = os.listdir()
print_file_dir(files)

f index.qmd
f topics.qmd~
f notes.qmd
f _quarto.yml
f notes.qmd~
f day4.org~
f push
f styles.css
f trainer.qmd
d .quarto
f index.qmd~
f day4.org
f _quarto.yml~
d _site
f .gitignore
f module1-day1.ipynb
f module1-day2.ipynb
f topics.qmd
f about.qmd
f module1-day3.ipynb
f Makefile~
f Makefile
d .ipynb_checkpoints
f module1-day4.ipynb

def longlistdir(path):
    files = os.listdir(path)
    print_file_dir(files)

longlistdir("/home/vikrant/trainings/")

d 2023
d 2018
d nakul
d day5.org
d 2022
d hello.py
d day5.org~
d 2024
d selenium_code_for_team
d 2020
d trainingvenv
d 2021
d 2019
d 2025
d 2017
d indexdata.xlsx
d selenium_venv

os.path.isfile("x.txt")

False

os.path.isdir("Desktop") # this is relative path

False

os.path.isdir("/home/vikrant/Desktop/")

True

longlistdir(os.getcwd())

f index.qmd
f topics.qmd~
f notes.qmd
f _quarto.yml
f notes.qmd~
f day4.org~
f push
f styles.css
f trainer.qmd
d .quarto
f index.qmd~
f day4.org
f _quarto.yml~
d _site
f .gitignore
f module1-day1.ipynb
f module1-day2.ipynb
f topics.qmd
f about.qmd
f module1-day3.ipynb
f Makefile~
f Makefile
d .ipynb_checkpoints
f module1-day4.ipynb

def longlistdir_(path):
    files = os.listdir(path)
    for filename in files:
        filepath = os.path.join(path, filename)
        if os.path.isfile(filepath):
            print("f", filename)
        else:
            print("d", filename)

longlistdir_("/home/vikrant/trainings/")

d 2023
d 2018
d nakul
f day5.org
d 2022
f hello.py
f day5.org~
d 2024
d selenium_code_for_team
d 2020
d trainingvenv
d 2021
d 2019
d 2025
d 2017
f indexdata.xlsx
d selenium_venv

Homework

Write function nrandoms which generates n random numbers bewteen 0 to 1.

>>> nrandoms(5)
[0.3180185315734232, 0.19816999876078534, 0.6549675992714722, 0.2966844056529988, 0.5773329096505485]

Write a function findlens which finds lengths of every word from a given list of words.

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

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

>>> find_words_of_len(words, 3)
['one', 'two', 'six']

Write a function findfiles which finds all files in given directory recursively with given extension.::

>>> findfiles("/var/", "log")
['/var/log/bootstrap.log',
'/var/log/alternatives.log',
'/var/log/dpkg.log',
'/var/log/apt/term.log',
'/var/log/apt/history.log']

Write a function greeting which greets randomly in variaus ways::

>>> greeting("Vikrant")
"Hello Vikrant"
>>> greeting("Vikrant")
"Namaste Vikrant"
>>> greeting("Vikrant")
"Good day Vikrant"
>>> greeting("Vikrant")
"Guten morgen Vikrant"