Splitting Cells and Counting Unique Values in Python List

Here, we need to split elements of a list and count the unique values from the resulting segments.

For example, given a list like ["a,b,c", "b,c,d" , e,f"], we want to extract each value, count only the unique ones, and return the result. Let’s examine different methods to achieve this, starting from the most efficient approach.

Using set()

We can directly use a set() to store unique values while splitting and iterating over the elements in the list.

# Input list
a = ["a,b,c", "b,c,d", "e,f"]

# Split elements and store unique values in a set
unique = set(value for item in a for value in item.split(","))

# Count the unique values
cnt = len(unique)
print(cnt)  

6

Explanation:

• We use a set comprehension to split each element of the list and store the unique values.
• Sets automatically handle duplicates, so only unique elements are retained.
• The length of the set gives the count of unique values.

Using itertools.chain

This method uses itertools.chain to flatten the split elements and then finds unique values using a set.

from itertools import chain

# Input list
a = ["a,b,c", "b,c,d", "e,f"]

# Flatten the split elements and store unique values in a set
unique = set(chain.from_iterable(item.split(",") for item in a))
cnt = len(unique)
print(cnt) 

6

Explanation:

• We use chain.from_iterable to flatten the list of split elements into a single iterable.
• A set is then used to remove duplicates.
• Finally, we calculate the length of the set to get the count of unique values.

Using list and converting to a set

This method first collects all values in a list, then converts it to a set to find the unique values.

# Input list
a = ["a,b,c", "b,c,d", "e,f"]

# Collect all values in a list
b = [value for item in a for value in item.split(",")]

# Convert the list to a set to get unique values
unique = set(b)

# Count the unique values
cnt = len(unique)
print(cnt)  

6

Explanation:

• We use a list comprehension to collect all the split values from the list.
• The list is then converted into a set to remove duplicates.
• Finally, the length of the set gives the count of unique values.

Using for loop

This method explicitly uses a for loop to split and add elements to a set for uniqueness.

# Input list
a = ["a,b,c", "b,c,d", "e,f"]

# Initialize an empty set
unique = set()

# Loop through each element and add split values to the set
for item in a:
    unique.update(item.split(","))

# Count the unique values
cnt = len(unique)
print(cnt) 

6

Explanation:

• We initialize an empty set to store unique values.
• Each element of the list is split, and the resulting parts are added to the set using the update method.
• The length of the set gives the total number of unique values.