Conditionals. The instruction if ... else ... allows programmers to tell Python to execute different segments of code depending on some the trutth value of a given logical condition. Common logical conditions consist in comparisons of two mathematical expressions through the operators
< (smaller than);
<= (smaller than or equal to);
> (greater than);
>= (greater than or equal to);
== (equal to);
Recall that = is an assignment, the logical operator testing the equality of two expressions is ==.
Comparing floating-point numbers. Due to the ever-present round-off errors, it is never a good idea comparing with == two floating point numbers, as the following code shows: A better solution is to fix some tolerance eps and asking that the distance between the two numbers is smaller than that: Of course in this case by "equal" we really mean "close enough to each other for our purposes".
Defining functions. What if we need to define, within Python, a function, say \(f(x)=\sin x-3x^4\text{?}\) the simplest solution is using the syntax as in the example below: In Python's jargon, these are called Anonymous functions.
