# How to Count Unique Values in a Python List?

There are several ways to count unique values in a Python list. Here are a few methods:

1. Using a Set:
``````my_list = [1, 2, 3, 3, 4, 4, 5, 6, 6, 7, 7, 7]
unique_values = set(my_list)
count = len(unique_values)
print(count)  # Output: 7``````

In this approach, we convert the list to a set, which automatically removes duplicate values, since sets only allow unique elements. Then, we use the `len()` function to get the count of unique values.

1. Using a Dictionary:
``````my_list = [1, 2, 3, 3, 4, 4, 5, 6, 6, 7, 7, 7]
unique_dict = {}
for value in my_list:
unique_dict[value] = True
count = len(unique_dict)
print(count)  # Output: 7``````

In this approach, we iterate through the list and use a dictionary to keep track of unique values as keys. Since dictionary keys are unique, this approach allows us to count the unique values. We then use the `len()` function to get the count of unique values.

1. Using the Counter class from the collections module:
``````from collections import Counter

my_list = [1, 2, 3, 3, 4, 4, 5, 6, 6, 7, 7, 7]
count_dict = Counter(my_list)
count = len(count_dict)
print(count)  # Output: 7``````

In this approach, we use the `Counter` class from the `collections` module, which is specifically designed for counting elements in collections. We pass the list to the `Counter` class, which returns a dictionary-like object with elements as keys and their counts as values. We then use the `len()` function to get the count of unique values, which is the length of the `Counter` object.