Python Variables

What Are Variables in Python?

In Python programming, variables serve as symbolic names assigned to data values. They act as containers for storing information that can be referenced and manipulated throughout a program.

Creating Variables

Unlike some other languages, Python does not require an explicit declaration to create a variable. A variable is instantiated automatically upon assignment:

x = 5
y = "John"
print(x)
print(y)

In this example, x is assigned an integer value, while y holds a string.

Dynamic Typing in Python

Python is dynamically typed, which means the type of a variable is interpreted during runtime. Moreover, a variable can be reassigned to a different data type:

x = 4       # x is of type int
x = "Sally" # x is now of type str
print(x)

This flexibility allows developers to write concise and readable code.

Casting: Explicit Type Conversion

Although Python handles type inference automatically, developers may occasionally need to specify data types explicitly using casting:

x = str(3)    # x will be '3' (string)
y = int(3)    # y will be 3 (integer)
z = float(3)  # z will be 3.0 (float)

Casting is useful when precise control over variable types is required.

Determining a Variable’s Data Type

To identify the data type of a variable, Python offers the built-in type() function:

x = 5
y = "John"
print(type(x))
print(type(y))

This is particularly helpful for debugging and ensuring that operations are performed on compatible data types.

String Declaration: Single vs. Double Quotes

Python allows string values to be enclosed in either single (') or double (") quotes. Both approaches are syntactically valid:

x = "John"
# is equivalent to:
x = 'John'

This duality provides flexibility when working with strings that contain quotes themselves.

Variable Names Are Case-Sensitive

Python treats uppercase and lowercase characters as distinct in variable names. As such, the following are interpreted as two separate variables:

a = 4
A = "Sally"

Here, a and A refer to completely different memory locations.

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