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Converting all object-typed columns to categorical type in Pandas DataFrame

schedule Aug 10, 2023
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Consider the following DataFrame where all the columns are of type `object`:

``` import pandas as pddf = pd.DataFrame({"A":[3,4], "B":[5,6]}, dtype="object")df A B0 3 51 4 6 ```

Solution

To convert `object`-typed columns to categorical:

``` list_str_obj_cols = df.columns[df.dtypes == "object"].tolist()for str_obj_col in list_str_obj_cols: df[str_obj_col] = df[str_obj_col].astype("category")df.dtypes A categoryB categorydtype: object ```

Explanation

We first obtain a list of the column labels where the column is of type `object`:

``` list_str_obj_cols = df.columns[df.dtypes == "object"].tolist()list_str_obj_cols ['A', 'B'] ```

We then iterate over this list and perform the type conversion using `astype("category")`.

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