my_list = []
my_list.append(1) #[1]
my_list.pop() # 1 []

for item in my_list:
    print(item)

my_list = [0] *5
print(my_list)

[0, 0, 0, 0, 0]

my_list = [1,2,3,4,5]
reversed_list = my_list[::-1]

print(reversed_list)

[5, 4, 3, 2, 1]

my_list = [1,2,3,4,5]
my_list.reverse()

print(my_list)

[5, 4, 3, 2, 1]

my_list = [1,2,3,4,5]
sub_list = my_list[2:4]

print(sub_list)

[3, 4]

my_list = [1,5,4,2,0,9,5,3,0]
sorted_list = sorted(my_list)
print(sorted_list)

[0, 0, 1, 2, 3, 4, 5, 5, 9]

my_list = [1,5,4,2,0,9,5,3,0]
my_list.sort()
print(my_list)

[0, 0, 1, 2, 3, 4, 5, 5, 9]

my_list = [["a",10],["b",5],["c",100]]

def get_second_element(element):
    return element[1]

my_list.sort(key=get_second_element,reverse=True)
print(my_list)

[['c', 100], ['a', 10], ['b', 5]]

lambda parameters: expression

my_list = [["a",10],["b",5],["c",100]]

my_list.sort(key=lambda x:x[1],reverse=True)
print(my_list)

[['c', 100], ['a', 10], ['b', 5]]

my_list= [['c', 100], ['a', 10], ['b', 5]]

# Map the first element of each sublist to a new list
new_list = [x[0] for x in my_list]
print(new_list)

my_list = [['c', 100], ['a', 10], ['b', 5]]

def get_first_element(element):
    return element[0]

new_list = list(map(get_first_element,my_list))
print(new_list)

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

my_list = [['c', 100], ['a', 10], ['b', 5]]
new_list = list(map(lambda x:x[0] ,my_list))
print(new_list)

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

my_dict = {
    "key1":1,
    "key2":2,
    "key3":3,
    "key4":4,
    "key5":5,
}

print(my_dict)
print(my_dict["key3"])

my_dict["key6"] = 6
print(my_dict)

del my_dict["key6"]
print(my_dict)

print("key4" in my_dict)
print("key6" in my_dict)

for key,value in my_dict.items():
    print(f"{key}-{value}", end=",")

{'key1': 1, 'key2': 2, 'key3': 3, 'key4': 4, 'key5': 5}
3
{'key1': 1, 'key2': 2, 'key3': 3, 'key4': 4, 'key5': 5, 'key6': 6}
{'key1': 1, 'key2': 2, 'key3': 3, 'key4': 4, 'key5': 5}
True
False
key1-1,key2-2,key3-3,key4-4,key5-5,

my_set = {1,2,3,4,5}
print(my_set)

my_set.add(6)
print(my_set)

my_set.remove(6)
print(my_set)

print(5 in my_set)
print(6 in my_set)

for item in my_set:
    print(f"{item}",end=",")

{1, 2, 3, 4, 5}
{1, 2, 3, 4, 5, 6}
{1, 2, 3, 4, 5}
True
False
1,2,3,4,5,

my_tuple = (1,2,3,4,5)
print(my_tuple)

print(my_tuple[3])

for item in my_tuple:
    print(item,end=",")

(1, 2, 3, 4, 5)
4
1,2,3,4,5,

from collections import deque

my_deque = deque([1,2,3,4,5])
print(my_deque)

my_deque.append(6)
print(my_deque)

print(my_deque.pop())
print(my_deque)

my_deque.appendleft(0)
print(my_deque)

print(my_deque.popleft())
print(my_deque)

for val in my_deque:
    print(val,end=",")

deque([1, 2, 3, 4, 5])
deque([1, 2, 3, 4, 5, 6])
6
deque([1, 2, 3, 4, 5])
deque([0, 1, 2, 3, 4, 5])
0
deque([1, 2, 3, 4, 5])
1,2,3,4,5,

from collections import Counter

my_counter = Counter([1,2,3,4,5,4,2,5,1,2,2,1,2,2])
print(my_counter)

print(my_counter[2])

my_counter[6] = 100
print(my_counter)

del my_counter[6]
print(my_counter)

for key,value in my_counter.items():
    print(f"{key}-{value}",end=",")

Counter({2: 6, 1: 3, 4: 2, 5: 2, 3: 1})
6
Counter({6: 100, 2: 6, 1: 3, 4: 2, 5: 2, 3: 1})
Counter({2: 6, 1: 3, 4: 2, 5: 2, 3: 1})
1-3,2-6,3-1,4-2,5-2,

import heapq

my_heap = [5,1,4,2,1,3,0,2]
heapq.heapify(my_heap)

print(my_heap)
smallest = my_heap[0]
print(smallest)

heapq.heappush(my_heap,3)
print(my_heap)

print(heapq.heappop(my_heap))
print(my_heap)

for item in my_heap:
    print(item,end=",")

[0, 1, 3, 2, 1, 5, 4, 2]
0
[0, 1, 3, 2, 1, 5, 4, 2, 3]
0
[1, 1, 3, 2, 3, 5, 4, 2]
1,1,3,2,3,5,4,2,

Lecture 3 Collections¶

Lists¶

CRUD¶

Init a list with default values¶

Reversing the list (Returns a new list)¶

Reversing the list in place¶

Create a sub list from the existing list¶

Sorting a list and create a new list¶

sorting the list in place¶

Sorting via custom comparator in place¶

Sorting via lamda to void function creation and use inline¶

Mapping the elements to new elements¶

Doing the same using map¶

Using both map and lamda¶

Dict¶

Set¶

tuple¶

deque¶

Counter¶

heapq¶