# 5.5. Random numbers¶

If you give most computer programs the same input multiple times,
they will always produce exactly the same output. Programs like this
are said to be *deterministic*. Determinism is usually a good thing,
since we expect the same calculation to yield the same result. For some
applications, though, we want the computer to be unpredictable. Games
are an obvious example, but there are more.

Making a program truly nondeterministic turns out to be no easy task, but
there are ways to make programs at least seem nondeterministic. One way is
to use *algorithms* that generate *pseudorandom* numbers. Pseudorandom
numbers are not truly random because they are generated by a deterministic
computation, but just by looking at the numbers it is all but impossible to
distinguish them from a truly random set.

The `random`

module provides functions that generate
pseudorandom numbers (which I will simply call “random” from here on).

The function `random`

returns a random float between 0.0 and
1.0 (including 0.0 but not 1.0). Each time you call `random`

,
you get the next number in a long series. To see a sample, run this
loop:

This program produces the following list of 10 random numbers between 0.0 and up to but not including 1.0. Notice how the numbers you ran above are different than the ones below, which were generated earlier.

```
0.11132867921152356
0.5950949227890241
0.04820265884996877
0.841003109276478
0.997914947094958
0.04842330803368111
0.7416295948208405
0.510535245390327
0.27447040171978143
0.028511805472785867
```

**Run the program more than once and see what numbers you get.**

The `random`

function is only one of many functions that
handle random numbers. The function `randint`

takes the
parameters `low`

and `high`

, and returns an
integer between `low`

and `high`

(including both).

To choose an element from a sequence at random, you can use
`choice`

:

The `random`

module also provides functions to generate
random values from continuous distributions including Gaussian,
exponential, gamma, and a few more.

p9-4: The ________ module provides functions that generate pseudorandom numbers

Construct a block of code that correctly generates a random integer between 1 and 100 (inclusive), then prints it out. Hint: there are two code blocks that are not used.

Construct a block of code that correctly generates a random number from the list called “nums”, then prints it out. Hint: there are four code blocks that are not used.