Module I - Day 2

Python Foundation

Nov-Jan 2025 batch, Vikrant Patil

Date: 18 Nov 2025

more built ins

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

len(nums)

int("556")

int(5.6)

float("78.5")

78.5

float(78)

78.0

str(78.8)

'78.8'

str(nums)

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

sum(nums)

max(nums)

min(nums)

sorted(nums) # this creates a new list with numbers in sorted order

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

nums = [4 , 3, 1, 7, 3, 9, 2]

sorted(nums) # it will sort and created new list , but original list remains as it is

[1, 2, 3, 3, 4, 7, 9]

nums

[4, 3, 1, 7, 3, 9, 2]

new_nums = [2, 3, 5, 1, 6, 7]

I restarted the kernel here so I lost all the variable that i had defined

nums

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

NameError: name 'nums' is not defined

nums = [4 , 3, 1, 7, 3, 9, 2]

sorted(nums)

[1, 2, 3, 3, 4, 7, 9]

sorted(nums, reverse=True) # reverse is called as named argument. it menas you have to give it always with name

[9, 7, 4, 3, 3, 2, 1]

there is another basic datatype which we didn’t talk… boolean it has two values True and False

sum(nums)/len(nums)

4.142857142857143

True

True

False

False

Everythng in Python is an object! it means functions, classes, integers , floats..everythings is treated in same fashion when it comes to variable

x = 10
y = x # alias to x

mylen = len # alias to len!

mylen(nums)

methods

A function defined inside the object which can manipulate the object’s data is called as methods.

empty = []

empty.append(0) # a fun

empty

[0]

empty.append(1)

empty

[0, 1]

empty.insert(0, 4)

empty

[4, 0, 1]

x = 10
y = x
x = 30

nums

[4, 3, 1, 7, 3, 9, 2]

nums[0] = -1

nums.append(5)

empty.pop() # remove last item and retun it!

empty

[4, 0]

x = empty.pop() # this will remove last item from empty and store it in x

empty

[4]

help(empty.pop)

Help on built-in function pop:

pop(index=-1, /) method of builtins.list instance
    Remove and return item at index (default last).

    Raises IndexError if list is empty or index is out of range.

nums

[-1, 3, 1, 7, 3, 9, 2, 5]

nums.pop(0)

-1

nums

[3, 1, 7, 3, 9, 2, 5]

nums.insert(2, -5) # first argument is index at which we want to insert and second arg is the value to be inserted

nums

[3, 1, -5, 2, 7, 3, 9, 2, 5]

[1, 2, 3, 4] + [-1, -1, -1]

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

ones = [1]*5
twos = [2]*5

ones

[1, 1, 1, 1, 1]

twos

[2, 2, 2, 2, 2]

ones + twos

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

ones

[1, 1, 1, 1, 1]

twos

[2, 2, 2, 2, 2]

ones.extend(twos)

ones

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

twos

[2, 2, 2, 2, 2]

string methods

text = "Some text for testing methods"

text.capitalize()

'Some text for testing methods'

name = "vikrant"

name.capitalize()

'Vikrant'

name.upper()

'VIKRANT'

text.startswith("hello")

False

text

'Some text for testing methods'

text.lower()

'some text for testing methods'

text.endswith("methods")

True

text.strip()

'Some text for testing methods'

traling = "    this text has trailing white spaces    "

traling

'    this text has trailing white spaces    '

traling.strip()

'this text has trailing white spaces'

x # iterpreters help to developer ... show me what is this object

print(x)

mulitline = """this is line one
this is line 2"""

print(mulitline)

this is line one
this is line 2

mulitline

'this is line one\nthis is line 2'

line = "this is a line from csv file\n"

line.strip() # removes trailing whitespaces ..space, tab, new line

'this is a line from csv file'

text

'Some text for testing methods'

text.split() # by default it will split on white space

['Some', 'text', 'for', 'testing', 'methods']

text.split() # this will create list of wrods ... assumption is words are separated by white spaces!

['Some', 'text', 'for', 'testing', 'methods']

header = "symbol,value,high value,low value,volume"

columnsnames = header.split(",")

columnsnames

['symbol', 'value', 'high value', 'low value', 'volume']

if list of words is given how do you make statement out of it?

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

" ".join(words)

'one two three four five'

statement = " ".join(words)

say_text = 'hello, I want to say something... and it it "python"'

say_text

'hello, I want to say something... and it it "python"'

say_text.split()

['hello,',
 'I',
 'want',
 'to',
 'say',
 'something...',
 'and',
 'it',
 'it',
 '"python"']

say_text.split(",")

['hello', ' I want to say something... and it it "python"']

say_text.split(".")

['hello, I want to say something', '', '', ' and it it "python"']

words

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

" ".join(words)

'one two three four five'

"".join(words)

'onetwothreefourfive'

"/".join(words)

'one/two/three/four/five'

",".join(words)

'one,two,three,four,five'

problems

a filename is given is a variable filename . how will you find extension of that file?

filename = "hello.txt"

filename.split(".")

['hello', 'txt']

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

'txt'

list slicing

nums

[3, 1, -5, -5, 2, 7, 3, 9, 2, 5]

nums[0]

nums[1]

nums[1:5] # start at index 1 and end at index 5(exluded!)

[1, -5, -5, 2]

range(10)

range(0, 10)

naturals = list(range(10))

naturals

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

natural[5:] # what ever yoi don't give it will default

[5, 6, 7, 8, 9]

naturals[3:] # drop first 3..and give rest

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

naturals[:3] # take first three

[0, 1, 2]

naturals[::] # copy

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

naturals[::2]

[0, 2, 4, 6, 8]

natural[1:8:3] # start:end:step

[1, 4, 7]

natural[::-1] # reverse

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

x = 10
y = x # this is not copy. linking the

ones = [1, 1, 1]
copy_ones = ones

copy_ones

[1, 1, 1]

ones.append(0)

ones

[1, 1, 1, 0]

copy_ones

[1, 1, 1, 0]

real_copy = ones[::]

real_copy

[1, 1, 1, 0]

ones.pop()

ones

[1, 1, 1]

real_copy

[1, 1, 1, 0]

ones

[1, 1, 1]

copy_ones

[1, 1, 1]

copy_ones.append(-1)

copy_ones

[1, 1, 1, -1]

ones

[1, 1, 1, -1]

real_copy

[1, 1, 1, 0]

it_is_ok_to_hav_big_name_but_meaningful = 1

list(range(1, 9, 2)) # start, end, step

[1, 3, 5, 7]

list(range(10)) # only end! start is taken as 0 and step as 1

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

list(range(1,10))

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

functions

def square(x): # code block start from next line
    s = x * x
    return s

the moment above cell is executed, there will be a variable with name square created!

square

<function __main__.square(x)>

square()

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[140], line 1
----> 1 square()

TypeError: square() missing 1 required positional argument: 'x'

square(5)

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

say_hello("python")

Hello python

square(5)

def foo():
    pass # empty statment

foo

<function __main__.foo()>

foo()

any function that does not return , it actually returns None object

del sqaure # you delete variables using del statement

sqr5 = square(5)

x = 10

sqr5

val = say_hello("vikrant")

Hello vikrant

val

val

print(val)

None

val

def square(x): # code block start from next line
    s = x * x
    return s

x = 10

square(56)

def func(a):
    a = 50

a = 10
func(a)

x = 10
x = 20

Homework

Write a function count_digits which will return number of digits from given integer.
Write a function sum_naturals which will return sum of first n natural numbers. hint: make use of range and sum
Write a function symmetric_join which will join a given list with its own mirror. Here is example
```
symmetric_join([1,2,34])
[1, 2, 34, 34, 2, 1]
```