Any data that can be referred to in a Python code is considered an object. Objects are used to represent everything from atomic data, such as numbers, to very complex data structures, such as multidimensional arrays, database connections, and documents in several formats.

At the root of the object hierarchy are the numeric data types. These include the following:

The following table has examples of literals (that is, constants) for each data type:

The imaginary unit is represented by j, but only if it follows a number literal (otherwise, it represents the variable named j). So, to represent the imaginary unit we must use 1j and the complex zero is 0j. The real and imaginary part of a complex number are always stored as double-precision floating-point values.

The assignment statement is used to store values in variables, as follows:

a = 3
b = 2.28
c = 12
d = 1+2j

Python supports multiple simultaneous assignments of values, so the previous four lines of code could be equivalently written in a single line as follows:

a, b, c, d = 3, 2.28, 12, 1+2j

In a multiple assignment, all expressions in the right-hand side are evaluated before the assignments are made. For example, a common idiom to exchange the values of two variables is as follows:

v, w = w, v

As an exercise, the reader can try to predict the result of the following statement, given the preceding variable assignments:

a, b, c = a + b, c + d, a * b * c * d
print a, b, c, d

The following example shows how to compute the two solutions of a quadratic equation:

a, b, c = 2., -1., -4.
x1, x2 = .5 * (-b - (b ** 2 - 4 * a * c) ** 0.5), .5 * (-b + (b ** 2 - 4 * a * c) ** 0.5)
print x1, x2

Note that we force the variables a, b, and c to be floating-point values by using a decimal point. This is good practice when performing numerical computations. The following table contains a partial list of Python operators:

from __future__ import division

Arithmetic operators follow the rules for the order of operations that may be altered with the use of parenthesis. Comparison operators have lower precedence than arithmetic operators, and the or, and, and not operators have even lower precedence. So, an expression like the following one produces the expected result:

2 + 3 < 5 ** 2 and 4 * 3 != 13

In other words, the preceding command line is parsed as follows:

(((2 + 3) < (5 ** 2)) and ((4 * 3) != 13))

The logical operators and and or short circuit, so, for example, the second comparison is never evaluated in the command:

2 < 3 or 4 > 5

The precedence rules for the bitwise and shift operators may not be as intuitive, so it is recommended to always use parenthesis to specify the order of operations, which also adds clarity to the code.

Python also supports augmented assignments. For example, the following command lines first assign the value 5 to a, and then increment the value of a by one:

a = 5
a += 1

All Python operators have a corresponding augmented assignment statement. The general semantic for any operator $ is the following statement:

v $= <expression>

The preceding statement is equivalent to the following:

v = v $ (<expression>)