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[polars] Fetch the FRED CSV with requests before parsing it #647

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mmcky merged 1 commit into from
Oct 13, 2026
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[polars] Fetch the FRED CSV with requests before parsing it #647

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8 changes: 6 additions & 2 deletions lectures/polars.md
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Expand Up @@ -544,7 +544,8 @@ As in {doc}`pandas`, Python makes it straightforward to query online databases.

An important database for economists is [FRED](https://fred.stlouisfed.org/) --- a vast collection of time series data maintained by the St. Louis Fed.

Polars' `read_csv` can fetch data from a URL directly.
We download the CSV file with [requests](https://requests.readthedocs.io/en/latest/)
and pass its contents to Polars' `read_csv`.

We use `try_parse_dates=True` to parse the date column automatically

Expand All @@ -564,7 +565,10 @@ fred_url = ('https://fred.stlouisfed.org/graph/fredgraph.csv?'
'fgst=lin&fgsnd=2020-02-01&line_index=1&'
'transformation=lin&vintage_date=2024-07-29&'
'revision_date=2024-07-29&nd=1948-01-01')
data = pl.read_csv(fred_url, try_parse_dates=True)
import requests
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r = requests.get(fred_url)
data = pl.read_csv(r.content, try_parse_dates=True)
```

Let's inspect the first few rows
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