website/content/blog/iterativecsv.md

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2020-04-12 02:10:19 +00:00
---
title: "Iteratively Read CSV"
date: 2020-04-11T21:34:33-04:00
draft: false
tags: ["python"]
---
If you want to analyze a CSV dataset that is larger than the space available in RAM, then you can iteratively process each observation and store/calculate only what you need. There is a way to do this in standard Python as well as the popular library Pandas.
## Standard Library
```python
import csv
with open('/path/to/data.csv', newline='') as csvfile:
reader = csv.reader(csvfile, delimeter=',')
for row in reader:
for column in row:
do_something()
```
## Pandas
Pandas is slightly different in where you specify a `chunksize` which is the number of rows per chunk and you get a pandas dataframe with that many rows
```python
import pandas as pd
chunksize = 100
for chunk in pd.read_csv('/path/to/data.csv', chunksize=chunksize):
do_something(chunk)
```