Python Objects, Variables and Data Types

Everything in Python is an object. Each object has identity, a type, and a value. The identity refers to the address and does not change.

The type can be any of the following:

  1. None: This represents the absence of a value.
  2. Numbers: Python has three types of numbers: Integer, Floating Point and Complex.
  3. Sequences: These are ordered collections of elements. There are three types of sequences in Python: String, Tuples and Lists.
  4. Sets: This is an unordered collection of elements.

Numbers

Integers: They do not have any fractional part.

Floating point numbers: That do have a fractional part.

Complex numbers: The numbers having a real and an imaginary part.

Strings

In Python, a string is a predefined object which contains characters. The value can be printed by using the print function. The value at a particular location of a string can be displayed using indexing. The index of the first location is 0. So, name[0] would print the first letter of the string, which is J.

name = "John"
print(name)
print(name[0])

Length

The length of a string can be found by calling the len function. len(str) returns the length of the string.

Concatenation

The + operator concatenates the strings.

Lists

A list is a collection of objects. It is the most general sequence provided by the language. Unlike strings, lists are mutable. That is, an element at a particular position can be changed in a list. A list is useful in dealing with homogeneous and heterogeneous sequences.