How to keep unique items from a collection of similar items in a list? [duplicate]

Answer 1

if you work with numpy arrays, you could use a simple diff filter to mask repeated elements:

import numpy as np

a = np.array([5,5,5,5,3,3,2,2,2,2,5,5,5,2,2,2,2,2])

mask = np.ones(a.shape).astype(np.bool_)
mask[1:] = np.diff(a).astype(np.bool_) # prepend a 'True', adjust if not 1D

b = a[mask]
# [5 3 2 5 2]

Answer 2

Other than just doing a for loop you could use itertools groupby:

import itertools

a = [5,5,5,5,3,3,2,2,2,2,5,5,5,2,2,2,2,2]
b = [x[0] for x in itertools.groupby(a)]  # [5, 3, 2, 5, 2]

Documentation for this can be found here: https://docs.python.org/3/library/itertools.html#itertools.groupby

EDIT: Some clarification. The reason this is able to count re-occurrences in the list is explained by this paragraph in the documentation (emphasis mine):

The operation of groupby() is similar to the uniq filter in Unix. It generates a break or new group every time the value of the key function changes [...]

Answer 3

Bro u solve this problem without any iterator using list comprehensive

a = [5,5,5,5,3,3,2,2,2,2,5,5,5,2,2,2,2,2]
b = [a[i] for i in range(len(a)) if a[i]! = a[i-1]]
Print(b)
Output is b = [5,3,2,5,2]