Python Tutorials - Herong's Tutorial Examples - v2.15, by Herong Yang
What Is Variable
This section provides a quick introduction variables. A variable in Python is a symbolic name of a data object.
What Is Variable? A variable in Python is a symbolic name of a data object. Or you can say that a variable is an object name.
There several important features about Python variables.
1. An object can have 0, 1, or many names.
# create an object with no name assigned >>> 'apple' 'apple' # create an object and assign a name "x" >>> x = 'apple' # assign the object named "x" with another name "y" >>> y = x
2. A variable can also be considered as an storage for a reference or a pointer to the object.
# create an object with no reference stored >>> 'apple' 'apple' # create an object with reference stored in "x" >>> x = 'apple' # copy the reference in "x" to "y" >>> y = x
3. Its object value is used, when a variable is being operated.
# variable "x" is referring to "int" object for integer 3 >>> x = 3 # object's value 3 is being operated: 3*3 >>> x*x 9
4. a variable must be assigned (defined) with an object, before using it in operations.
# variable "y" has not been assigned with any object >>> y*y NameError: name 'y' is not defined
5. Variable names are case sensitive.
# 'x' and 'X' are 2 different variables >>> x = 3 >>> X*X NameError: name 'X' is not defined
6. A variable can be reassigned to another object of any data type at any time.
# create a "str" object and assign a name "x" >>> x = 'apple' # "x" is reassigned to another object >>> x = [9, 1, 1]
Table of Contents
►Variables, Operations and Expressions
Conditional Expression - Ternary Operation
Assignment Expression - Walrus Operation
Function Statement and Function Call
List, Set and Dictionary Comprehensions
Packages and Package Directories
"pathlib" - Object-Oriented Filesystem Paths
"pip" - Package Installer for Python
SciPy.org - Python Libraries for Science
pandas - Data Analysis and Manipulation
Anaconda - Python Environment Manager