File Handling Like a Pro

How Data Engineers read, write, and organize files at scale.

Welcome to Zero2DataEngineer — Week 3, Day 3

A real data engineer doesn’t say:

“Let me just load this CSV and print the head.”

They say:

“Let’s structure this folder, validate file size, and ingest in chunks with logging.”

Today’s lesson:
Python for production-grade file handling.

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Files You’ll Actually Handle in the Wild

You’re not reading files for fun.
You’re turning them into clean, usable, repeatable pipeline inputs.

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Real Example: Chunk Reading a Large CSV

import pandas as pd

chunks = pd.read_csv("big_sales.csv", chunksize=50000)

for i, chunk in enumerate(chunks):
    cleaned = chunk.dropna(subset=["customer_id"])
    cleaned.to_csv(f"cleaned_sales_part_{i}.csv", index=False)

This is how DEs handle:

• Large files without crashing memory

• Splitting clean output into batches

• Ensuring pipeline resiliency