🐍 Python Data Types

👨‍🏫 Vikesh K
📓 Lab 01

💡 A journey of a thousand miles begins with a single step- Chinese Proverb 💡

📝Lab Agenda

• Variables

  • Python keywords

• Data Types

  • Properties

  • Conversion

• OS Package

  • import

  • installation

• Exercises

Theory

Variables store values and keep code organized.

This process of storing something in a variable is often called variable assignment, or simply “assignment” for short. You can assign almost anything to a variable.

x = 3 
x

3

You can then use the stored values for calculations

y = x + 10
y

13

print() allows you to see the values of the variables

pue = 45
print(pue)

45

In case of multiple code line in jupyter if you don’t use the print() command, only the last code line will be shown in the output

x = 3 
y = 'Hello'

# show output
x
y

'Hello'

x = 4
x = 5

# show output
print(x)
print(y)

5
Hello

type() tells you the data type of the variable

print(type(x))
print(type(y))

<class 'int'>
<class 'str'>

The breadth of a rectangle is 10 and length is 11. What is the area and the perimeter of the rectangle?

Calculate the area and perimeter and then take the breadth as 13 and length as 15 and recalculate the values. Calculate this in the normal manner and using proper variables

Normal way to calculate

area = 8 * 9
print("the area is:", area)

perimeter = 2 * (8 + 9)
print("the perimeter is:", perimeter)

the area is: 72
the perimeter is: 34

Using variables

# define the length and breadth 
length = 8
breadth = 9

area = length * breadth 
print("the area is:", area)

perimeter = 2 * (length + breadth)
print("the perimeter is:", perimeter)

the area is: 72
the perimeter is: 34

Variable Summary

• Used to store information to be used in a computer program

• Has three components:

  • kind given by type(),

  • value given by print()

  • memory address given by id()

• There are rules in variable names:

  • Should start with alphabet or _ (underscore)

  • cannot start with a number

  • cannot have a space

  • can be alpha-numeric

  • should avoid keywords while naming

Python has got 4 major datatypes

int is for whole numbers: 1, 2, 4

# store the value
x = 2

# check the data type
print(type(x))

<class 'int'>

float is for numbers with decimals: 1.2, 3.14

# store the value
y = 2.0

# check the data type
print(type(y))

<class 'float'>

string is used for text: hello, my name

a = "Learning Python is fun"

print(a)
print(type(a))

Learning Python is fun
<class 'str'>

string can be saved using single quote or double quotes

p = 'Japan'

q = "Japan"

z = 'japan'

print(p)
print(q)

Japan
Japan

# are both are equal?
p == q

True

case matters in Python`

# are both are equal?
p == z

False

bool is used for True/ False

p = True
q = False

# check the data type
print(type(p))
print(type(q))

<class 'bool'>
<class 'bool'>

You can convert one datatype into another

• The conversion can be done using int(), float(), bool(), str()

• There will be some exceptions, like a string can’t be converted to a number, however a number can be

x = 2

print(x)
print(type(x))

2
<class 'int'>

float(x)

2.0

h = '45'
print(h)
print(type(h))

45
<class 'str'>

Check the type with int() function

type(int(h))

int

type(float(x))

float

type(x)

int

Change the type to float

x = float(x)

type(x)

float

y = 5
print(y)
print(type(y))

5
<class 'int'>

x = '5'
print(type(x))

<class 'str'>

int to float conversion

x = float(x)
print(x)
print(type(x))

5.0
<class 'float'>

float to int conversion

y = 2.9
print(y)
print(type(y))

2.9
<class 'float'>

Warning

Be careful on changing a float to an int. Numbers after decimal point will be dropped

y = int(y)

print(y)
print(type(y))

2
<class 'int'>

y = 3.5

y = int(y)

print(y)

3

float to bool conversion

• 0 always converts to False

• Any value other than 0 is True, whether positive or negative

y = -2.3
print(y)
print(type(y))

-2.3
<class 'float'>

bool(y)

True

z = 0
print(z)
print(type(z))

0
<class 'int'>

z = bool(z) 

print(z)
print(type(z))

False
<class 'bool'>

Bool to Int

int(True)

1

int(False)

0

Data Type Summary

Source: Jovian ML

Data type	Example
float	3.14
int	3
string	‘john’
bool	True, False

• Every data-type has a specific property in Python and are used to represent different kinds of data

• One can check for the data type of an item using type(item)

• One can convert one data type into another using : int(), str(), float() and bool()

Packages in Python

Note

In Python, whenever you want to run/launch a package, you need to import it.

In the smart phone analogy, this is equal to tapping on an app to start it. You would have pre-installed apps and apps that you need to install. Remember, like in a phone’s pre-installed apps, os is one of the pre-installed apps.**

You won’t get any message if a package is imported successfully. Only if you do a wrong loading, error message will be shown

While importing you can also use alias, by the command as, this is often done. It helps to make the code crisp

# import the module
import os
print("The code ran")

The code ran

You will see an error message if you load something wrongly. Example: loading a non-existing package

import os
print("The code ran")

The code ran

Note

Installing a new package

We can install a new package using pip. The most easiest way is to install a package within the Jupyter notebook.

The syntax is !pip install packagename

Installing plotly package

Let’s install a package and understand the process. Run the cell below

The below code will generate some text detailing the installation.If you get an error, please google for the answer. If you can’t figure it out, send me a note

# !pip install plotly

To check if the installation happened properly, running the below code should not give any error

# loading the package
import plotly
print("All ran properly")

All ran properly

Checking the installed version of a package

The syntax to check a version of the installed packages. packagename.__version__

# checking the version of pandas
import pandas as pd
print(pd.__version__)

2.2.0

# checking the version of numpy 
import numpy as np
print(np.__version__)

1.23.5

print(plotly.__version__)

5.9.0

The os package in python helps us interact with the os system

What is my current working directory (folder) - cwd?

import os

os.getcwd() # get me the Current Working Directory (Folder)

'C:\\Users\\vkoul\\Desktop\\DA_Training_book\\pythonbook'

Can we see the files in the directory?

# os.listdir() # list directory

❓Exercises

Some of the exercises below are strech exercises, you may need to rely on Google to answer them. This should be a good experience of figuring out things on your own

Data Types

Q1 What is the type of the following: 2.0

# your code here 

Q2 What is the result of the following code segment: type(int(13.6))

# your code here 

Q3 What is the result of the following code segment: int(4.99)

# your code here 

Q4 What is the result of the following code segment: int(False)

# your code here 

Q5 What is the result of the following code segment: 1/3 ? What data type it is?

# your code here 

Q6 What is the data type of the `’3’``

# your code here 

Variables

Q1 What is the value of x after the following lines of code?
x = 2
x = x + 2

# your code here 

Q2 What would be the value of y in the following operation y = 2 + 5*4

# your code here 

Q3 What is the type of the variable x after the following: x = 2/2 ?

# your code here 

Strings

Q1 Is "China" and "china" same for python?

x = "China"
y = "china"

x == y

False

Q2 Is "japan" and 'japan' same for python?

# your code here 

Q3 How would you determine the length of the string: "japan"

# your code here 

Q4 What is the result of the following operation: '2'+'3' ?

# your code here 

Q5 What is the result of the following : str(2) + str(2) ?

# your code here 

Q6 If you executed name = 'Buzz', what would be the output of print(name[0:2])?

# your code here 

Q7 If you executed var = '01234567', what would be the result of print(var[::2])?

# your code here 

Q8 What is the result of the following: 'hello'.upper() ?

# your code here 

Q9 What is the result of the following: "123".replace("12", "pqr") ?

# your code here 

Q10 What is the result of "netherlands".find("land")?

# your code here 

Q10 How to reverse a string? x = "London"

# your code here 

🧠Points to remember

• The counting in Python starts from 0.

• We can check for a data-type using the type() function.

• Python can also do reverse count, it starts from -1.

• One can convert a data type into another using different functions int(), str(), float()

• float is for the decimal numbers

• You can do different operations on strings- .upper(), .replace(), .find()

• We can slice a string using [start:stop:steps] operation

  • Remember the stop is not inclusive

• Also, you can find the reverse of a string using string[::-1]

📚 Resources

• Read about the different functions in os module here

• Tutorial on how to use os module here

• Jupyter Notebook Markdown