How can I use dictionaries in Python to find duplicates in a list?

How can I use dictionaries in Python to find duplicates in a list?

You can use a dictionary to count occurrences of each item in the list. If the count is greater than 1, it's a duplicate.

Can you show me a code example?

Sure! Here's a simple example:

my_list = [1, 2, 3, 2, 4, 5, 1]
duplicates = {}

for item in my_list:
    if item in duplicates:
        duplicates[item] += 1
    else:
        duplicates[item] = 1

duplicates = {key: value for key, value in duplicates.items() if value > 1}
print(duplicates)

This will output {1: 2, 2: 2} indicating that 1 and 2 are duplicates.

What if I want just the duplicate values without counts?

You can modify the code to collect just the keys with a count greater than 1. Here's how:

my_list = [1, 2, 3, 2, 4, 5, 1]
duplicates = set()
seen = set()

for item in my_list:
    if item in seen:
        duplicates.add(item)
    else:
        seen.add(item)

print(list(duplicates))

This will give you a list of duplicates: [1, 2].