11.1.1.3 distinguish between data types in Python
11.1.1.4 convert data types of variables

Variables in Python. Data types. Converting data types of variables.

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Variables

hello = 'Hi'
hello2 = hello
print(hello2)

Rules for creating variables in Python:

• Variable names must start with a letter or underscore.
• Variable names cannot start with a number.
• A variable name can only contain letters, numbers, and underscores (A - z, 0-9, and _).
• Variable names are case sensitive (num, Num and NUM are three different variables).
• Reserved words (keywords) cannot be used to name a variable.

number = 10      # variable number of integer type assigns the value 10
pi = 3.14        # floating point pi is assigned the value 3.14
word = "Hello"   # variable word of string type assigns the value "Hello"
print(number, pi, word) # output values of variables

How define the data type of variable.

The function type() shows the data type of variables.

Example

lang = "Python" 
print(type(lang))     # <class 'str'>
amount = 15 
print(type(amount))   # <class 'int'>
height = 1.78 
print(type(height))   #<class 'float'>

You can see that python uses dynamic typing, that is, a variable can change the data type depending on the value assigned to it.

Variable can change value in a program. 

word = "Astana"
print("2017 - ", word)
print("2018 –", word)
word = "Nur-Sultan"
print("2019 –", word)
print("2020 –", word)
print("2021 –", word)

Output data:

2017 - Astana
2018 - Astana
2019 – Nur-Sultan
2020 – Nur-Sultan
2021 – Nur-Sultan

Converting data types

int(string) – convert string to int
float(string) – convert string to float
int(float) – convert floating point number to an integer
str(int) – convert integer to string
str(float) – convert floating point number to string
 

Questions:

1. What does it mean "data type"?

2. Name four data types.

3. Provide examples for each data type.

Exercises: 

Ex.1 Data types in Python (Author: Mr. Halil Mali - CS teacher of NIS Uralsk) 

Ex.2 Data types in Python

Tasks: