Python Array Duplicates Remover
Filter duplicate items from a Python list while maintaining their original insertion order.
How it Works
Removing duplicates is one of the most common data cleaning operations in software.
Casting a list to a set (`set(arr)`) removes duplicates but destroys the order of elements because sets are unordered.
To remove duplicates while preserving the order, we iterate through the list and track seen elements in a set, appending new ones to a result list.
Source Code
Efficient O(n) order-preserving unique elements accumulator.
def remove_duplicates(arr):
seen = set()
result = []
for item in arr:
if item not in seen:
seen.add(item)
result.append(item)
return result
sample_list = [1, 2, 2, 3, 4, 4, 1, 5]
print("Original:", sample_list)
print("Unique: ", remove_duplicates(sample_list))Original: [1, 2, 2, 3, 4, 4, 1, 5]
Unique: [1, 2, 3, 4, 5]Real-world Applications
- Sanitizing search history and transaction records logs
- Preparing unique data keys list for SQL queries
- Cleaning arrays for visualization mapping
Frequently Asked Questions
What is the fastest way to do this in Python 3.7+?
Since Python 3.7+ preserves dictionary insertion order, you can run `list(dict.fromkeys(arr))` to remove duplicates while maintaining order in a single optimized step.
More Examples
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