python-by-phitron

Day - 9: Swap, Count unique elements, extract elements, crete nested list using list comprehesion

List comprehension in Python
9.1 Swap two list elements in a list
9.2 Count unique elements in an list
9.3 Extract elements from a list
9.4 Create a list using list comprehension

Problem 1: Swaping to list elements

# Problem 1: Swaping to list elements
num_list = [17, 11, 12, 13, 14, 15, 16, 10]
temp = num_list[0]
num_list[0] = num_list[-1] # a[len(num_list) - 1]
num_list[-1] = temp
print(num_list)

Problem 2: Count unique elements in a list

# Problem 2: Count unique elements in an list
number_list = [1, 2, 2, 3, 3, 3, 4, 5, 6]
unique_number_list = []
unique_number_count = 0

for i in number_list:
   if i not in unique_number_list:
      unique_number_count = unique_number_count + 1
      unique_number_list.append(i)

print(unique_number_count)
print(unique_number_list)

Problem 3: Extract elements from a list

# Problem 3: Given a list, extract all elements whose frequency is greter than K.
# num_list = [4, 6, 4, 3, 3, 4, 3, 4, 3, 8] K = 3

num_list = [4, 6, 4, 3, 3, 4, 3, 4, 3, 8]
K = 3
result_list = []

for i in num_list:
   freq = num_list.count(i)
   if freq > K and i not in result_list:
      result_list.append(i)

print(result_list)

Create a list using list comprehension

# Problem 4: create the following list using list comprehension
# [[1, 2, 3, 4], [0, 2, 3, 4], [0, 1, 3, 4], [0, 1, 2, 4], [0, 1, 2, 3]]

num_list = [[j for j in range(5) if i !=j] for i in range(5)]
print(num_list)