Python Fundamentals

Python Fundamentals#

Almost all computer programs can be broken down into simple operations that are stringed together to perform complex tasks. In this section, we introduce core Python concepts and syntax that would be required to write Python programs.

Variables#

A key component of programming is the storage of information in a computer memory as variables. It is a way to assign small blocks of data with a label that is human-readable. We will start with simple numerical and string variables.

Numerics#

Numerical values can be of type float with decimals or of type int (integers). Floats are mainly used for arithmetic while integers are commonly used to count or index arrays.

x = 1
type(x)

int

We have created our first numerical variable x for which the computer as a pointer to the int value of 1. Note that we have also used two built-in Python methods: print and type.

The type method gets evaluated and returns the type of the object (see notes below). Input values for methods are always given between parentheses ().
The print method displays the result to screen.

Now let’s create a second variable y of numerical type float

y = 1.0
type(y)

float

Operations#

Here is a shortlist of standard arithmetic and logical operators that can be applied on numerical values (in order of priority of operation).

**: Power
% : Modulo
*: Multiplication
\: Division
+: Addition
-: Subtraction
==: Logical equal
> : Logical greater than
< : Logical smaller than

For example:

2**2 * 1.5 + 1 == 7.0

True

You can verify the result above by doing the operations in your head. It is important to keep in mind general rules of return types for numerical values.

Adding or subtracting integers yields an integer

type(x + x)

int

Multiplying or dividing integers yields a float

type(x / x)

float

Mix operations on integer and float always yield a float

type(x + y)

float

Strings#

Strings are text objects that contain characters (letters, numbers or symbols) isolated by single '' or double "" quotes. Both are acceptable but consistency throughout your code is preferable.

Here is a shortlist of useful methods that can be used on strings.

Adding

"hello" + " world"

'hello world'

Upper/lower and single word capitalization

"I" + " love ".upper() + "python".capitalize()

'I LOVE Python'

Upper case every word

"this is important".title()

'This Is Important'

Find sub-string within

"Long sentence with symbols #$%^&".find("sym")

Objects#

At the core, Python is an object-oriented programming (OOP) language. In short, a computer program is made up of many object variables that hold attributes and methods specific to itself. An object is also referred to as a Class. Think of it as a small machine that takes inputs, store values and does operations on request. Objects can interact with each other to form a program. Object-oriented programming allows for concise code that is easy to read and share with others - which explains the popularity of Python in the world of open-source.

oop

This is somewhat in contrast to imperative or procedural-based languages, such as C and Fortran. In an imperative framework, variables and functions are chained to form a series of computational steps executed in sequence, but variables themselves don’t do anything - they are simple container of data.

imperative

Python can also be written in a procedural way, but internally objects are always doing the work.

Take for example the numeric variables x introduced previously. While it appears to be a simple integer, it is still a Python object with methods. You can access the list of methods available to that specific object by typing . then the tab key after the variable

methods

In this case, the imag method of the integer would return the imaginary part of x (if it was a complex number). In a future section on Classes, you will be able to create your own type of object with custom methods. To be continued.