How to list, concatenate, and evaluate polars expressions?

Question

I would like to store in an object (a list, a dictionary or whatever) many different filters, and then be able to select the ones I want and evaluate them in the .filter() method. Below is an example:

# Sample DataFrame
df = pl.DataFrame(
    {"col_a": [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], "col_b": [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]}
)

# Set a couple of filters
filter_1 = pl.col("col_a") > 5
filter_2 = pl.col("col_b") > 8

# Apply filters: this works fine!
df_filtered = df.filter(filter_1 & filter_2)

# Concatenate filters
filters = [filter_1, filter_2]

# This won't work:
df.filter((" & ").join(filters))
df.filter((" | ").join(filters))

What would be the correct way of (" & ").join(filters) that will work?

Asked By: Guz

||

Source

Answer 1

You can use pl.all() or pl.any()

>>> df.filter(pl.all(filters))
shape: (2, 2)
┌───────┬───────┐
│ col_a | col_b │
│ ---   | ---   │
│ i64   | i64   │
╞═══════╪═══════╡
│ 9     | 9     │
│ 10    | 10    │
└───────┴───────┘

>>> df.filter(pl.any(filters))
shape: (5, 2)
┌───────┬───────┐
│ col_a | col_b │
│ ---   | ---   │
│ i64   | i64   │
╞═══════╪═══════╡
│ 6     | 6     │
│ 7     | 7     │
│ 8     | 8     │
│ 9     | 9     │
│ 10    | 10    │
└───────┴───────┘

Answered By: jqurious

How to list, concatenate, and evaluate polars expressions?

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