Tips and Tricks #133: Use Generators for Memory-Efficient Data Processing

Process large datasets without loading everything into memory using Python generators.

Code Snippet

# Before: Loads entire file into memory
def process_file_eager(filename):
    with open(filename) as f:
        lines = f.readlines()  # All in memory!
    return [parse_line(line) for line in lines]

# After: Streams data lazily
def process_file_lazy(filename):
    with open(filename) as f:
        for line in f:
            yield parse_line(line)

# Usage: Memory stays constant regardless of file size
for record in process_file_lazy("huge_file.csv"):
    process_record(record)

Why This Helps

• Constant memory usage regardless of data size
• Enables processing of files larger than RAM
• Integrates seamlessly with for loops and itertools

How to Test

• Monitor memory with memory_profiler
• Compare peak memory on large files

When to Use

ETL pipelines, log processing, any scenario with large sequential data.

Performance/Security Notes

Generators can only be iterated once. Use itertools.tee() if multiple passes needed.

References

• https://docs.python.org/3/howto/functional.html#generators

Try this tip in your next project and share your results in the comments!