Re: Starting Life in Python World 3: Lists

Introduction

topping = ['mushroom', 'pineapple', 'bacon', 'onion']
print(topping)
# ['mushroom', 'pineapple', 'bacon', 'onion']

• List is a compatible abstract data type. Data structure knowledge is required on how to realize it; can just directly understand and operate here, it is very easy after all.
• List in Python is somewhat similar to the array of languages like C (actually more convenient than the array operations, because of the integration of a large number of functions and methods)

Accessing list

1. Sequential access (pointer start at 0 and end at the last element position - 1)
2. Reverse order access ([-1] is the last element, and so on)

topping = ['mushroom', 'pineapple', 'bacon', 'onion']
print(topping[0])
print(topping[-1])

Output

mushroom
onion

Modify, insert and delete

These are permanent operations.
There is a deletion worth mentioning: the "stack" type pop deletion; the last element is popped in a non-specified position, and pop() is a "method" (pop the last element).

topping = ['mushroom', 'pineapple', 'bacon', 'onion']
del topping[0]
topping.remove('onion')
print(topping)
print()

topping = ['mushroom', 'pineapple', 'bacon', 'onion']
pop_topping = topping.pop()
print(pop_topping)
print(topping)

Output

['pineapple', 'bacon']

onion
['mushroom', 'pineapple', 'bacon']

Organization list

1. sort() sorting, which is divided into parameters with and without parameters
2. reverse() method implements reverse (directly reverse order of the list)

ordering = [4, 2, 1, 3]
ordering.sort()
ordering.sort(-1)
print(ordering)
print()

ordering.reverse()
print(ordering)
ordering.reverse()

Output

[4, 3, 2, 1]

[1, 2, 3, 4]

Getting the length of the list

The len() function gets the length of the list.

ordering = [4, 2, 1, 3]
print(len(ordering))

Output

4