Python

Variables

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It may be a good idea to segment the further pages into folders inside “Beginner_python”, so that you can easily come back to an organised structure of files.

In Python, a variable is a named location in memory that stores a value. Variables are used to store values that may change during the course of a program.

To create a variable in Python, you simply assign a value to a name.

Here we have three variables: x, y, and z. x is assigned the value 10, y is assigned the string “hello”, and z is assigned the boolean value True.

x = 10
y = "hello"
z = True

Since Python is a dynamically-typed language, this means that you don’t need to specify the data type of a variable when you create it. Python will automatically read the data type based on the value that is assigned to the variable.

You can use the type function to check the data type of a variable:

print(type(x))  
# Output: <class 'int'>
print(type(y))  
# Output: <class 'str'>
print(type(z))  
# Output: <class 'bool'>

We can also assign multiple variables at the same time:

a, b, c = 1, 2, 3
print(a)  # Output: 1
print(b)  # Output: 2
print(c)  # Output: 3

It’s important to choose descriptive and meaningful names for your variables to make your code easier to read and understand. Python has some naming conventions that you should follow when creating variables:

  • Variable names can only contain letters, numbers, and underscores.
  • Variable names cannot begin with a number.
  • Variable names are case-sensitive.
  • It is also a good idea to use snake_case for variable names, which means using all lowercase letters and separating words with underscores.

For example:

student_name = "Alice"
student_age = 21

In Python, there are a few reserved words that you cannot use as variable names. These include:

True, False, None, and, or, not, if, else, for, while, def, class, try.

It’s also a good idea to avoid using short, generic names for variables, as these can be difficult to understand and may cause confusion. Instead, use descriptive names that clearly reflect the purpose of the variable.

You can reassign a value to a variable at any time. To do this, simply use the assignment operator (=) and give the variable a new value. For example:

x = 10
print(x)  
# Output: 10

x = 20
print(x)  
# Output: 20

Reassigning a value to a variable will overwrite the previous value. It’s important to keep in mind that reassigning a different data type to a variable will change the data type of the variable. For example:

x = 10
print(type(x))  
# Output: <class 'int'>

x = "hello"
print(type(x))  
# Output: <class 'str'>

In the above code, the variable x is initially assigned the integer value 10, and its data type is int. When we reassign the value “hello” to x, the data type of x changes to become string.

Reassigning variables is a common operation in Python, and it is used to update the value of a variable based on the current state of the program. Just be sure to choose meaningful and descriptive names for your variables to make your code easier to read and understand.

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