- Engineering Notes

# Python Cheat Sheet

## Libraries

Before you can use libraries, you need to import them. For maths:

`import maths`

For random:

`import random`

If the library name i slong, such as for plotting, you can set a shortened name:

`import matplotlib.pyplot as plot`

### Useful random functions

To generate a random number, n, in the range 0 ≤ n < 1:

`n = random.random()`

To generate a random integer, n, in the range a ≤ n ≤ b:

`n = random.randint(a,b)`

Therefore, a function for rolling a standard six-sided die is:

`roll = random.randint(1,6)`

## Lists / Arrays

n number of data points can be stored in lists, where each data point is given an index address. The first term has address [0], and the last term has address [n-1]. Indexing can be done in negative: in this case, the last term has address [-1] and the first term has address [n].

### Defining Lists

To define lists manually:

```
Age = [18, 18, 19, 18, 17 ... ]
Colour = ['Blue', 'Green', 'Yellow' ...]
```

Note that you need to put strings in quote marks.

To define lists automatically as a list of integers from a range of a to b:

```
R = range(a, b+1)
A = []
for members in R:
A = A + [members]
```

To generate a list from a series of values, for example a set of random numbers:

```
for members in A:
members = random.randint(1,6)
die.append(members)
```

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