# index

Mutable, list can be modified

List needs to be in square bracket \[], for example: \[1,2,3,4,5] or \[‘a’,’b’,’c’] or \[1,2,3,’a’,’b’,’10’]

List is a sequence, iterable

l=\[‘a’,’b’,’c’]

l\[0]=“a”

l\[1]=“b”

l\[2]=“c”

It is zero based indexing, index starts from zero

List can be iterated through:

for i in l:

```
print\(i\)
```

Convert to List, use function list()

For example:

n=12345

list(n) becomes \[1,2,3,4,5]

List is an object, meaning it has methods and attributes that can be invoked

To see all methods, type

help(\<list variable>)

In Jupyter notebook, to see list of methods or attributes

Press shift key after enter \<list variable>.

\>>> squares = \[1, 4, 9, 16, 25]

\>>> squares

\[1, 4, 9, 16, 25]

\>>> squares\[0] # indexing returns the item

1

\>>> squares\[-1]

25

\>>> squares\[-3:] # slicing returns a new list

\[9, 16, 25]

\>>> squares\[:]

\[1, 4, 9, 16, 25]

\>>> squares + \[36, 49, 64, 81, 100]

\[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

cubes = \[1, 8, 27, 65, 125] # something's wrong here

\>>> 4 \*\* 3 # the cube of 4 is 64, not 65!

64

\>>> cubes\[3] = 64 # replace the wrong value

\>>> cubes \[1, 8, 27, 64, 125]

\>>> cubes.append(216) # add the cube of 6

\>>> cubes.append(7\*\*3) # and the cube of 7

\>>> cubes

\[1, 8, 27, 64, 125, 216, 343]

\>>> letters = \['a', 'b', 'c', 'd', 'e', 'f', 'g']

\>>> letters

\['a', 'b', 'c', 'd', 'e', 'f', 'g']

\>>> # replace some values

\>>> letters\[2:5] = \['C', 'D', 'E']

\>>> letters

\['a', 'b', 'C', 'D', 'E', 'f', 'g']

\>>> # now remove them

\>>> letters\[2:5] = \[]

\>>> letters

\['a', 'b', 'f', 'g']

\>>> # clear the list by replacing all the elements with an empty list

\>>> letters\[:] = \[]

\>>> letters

\[]

\>>> letters = \['a', 'b', 'c', 'd']

\>>> len(letters)

4

\>>> a = \['a', 'b', 'c']

\>>> n = \[1, 2, 3]

\>>> x = \[a, n]

\>>> x

\[\['a', 'b', 'c'], \[1, 2, 3]]

\>>> x\[0]

\['a', 'b', 'c']

\>>> x\[0]\[1]

‘b’

\# Fibonacci series:

\# the sum of two elements defines the next

a, b = 0, 1

fib=\[]

while True:

\# print(a)

```
if len\(fib\)&gt;=10:

    break

else:

    fib.append\(a\)

    a, b = b, a+b print\(fib\[-1\]\)
```