Store dataframes in a list by alignment in polars

pl.align_frames

You have two dataframes and want to store them in a list based on shared values in one column. Below are two dataframes; one with movie ratings and the other with duration.

Movie rating dataframe

shape: (4, 2)

Movie	Rating
str	f64
"Inception"	8.8
"The Revenant"	8.0
"The Wolf of Wall Street"	8.2
"Revolutionary Road"	7.3

Movie duration dataframe

shape: (4, 2)

Movie	Duration
str	i64
"The Fall Guy"	126
"The Revenant"	156
"La La Land"	128
"Revolutionary Road"	119

Align dataframes and store in list

To create a list of dataframes that contain movies featuring Leonardo DiCaprio, you can use the Polars expression pl.align_frames like this:

aligned_dfs = (pl.align_frames(rating_df,
                 duration_df,
                 on='Movie',
                 how='inner')
 )
aligned_dfs

[shape: (2, 2)
 ┌────────────────────┬────────┐
 │ Movie              ┆ Rating │
 │ ---                ┆ ---    │
 │ str                ┆ f64    │
 ╞════════════════════╪════════╡
 │ Revolutionary Road ┆ 7.3    │
 │ The Revenant       ┆ 8.0    │
 └────────────────────┴────────┘,
 shape: (2, 2)
 ┌────────────────────┬──────────┐
 │ Movie              ┆ Duration │
 │ ---                ┆ ---      │
 │ str                ┆ i64      │
 ╞════════════════════╪══════════╡
 │ Revolutionary Road ┆ 119      │
 │ The Revenant       ┆ 156      │
 └────────────────────┴──────────┘]

Now that you have a list of dataframes, you can access any one of them by index. For example, to get the first dataframe, do this:

aligned_dfs[0]

shape: (2, 2)

Movie	Rating
str	f64
"Revolutionary Road"	7.3
"The Revenant"	8.0

Notice that this movie rating dataframe is not the same as the original. This one only contains movies in which Leonardo DiCaprio appeared.

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