How can I check if a function parameter exists with Python?

Question

My code is:

def load_data(datafile, categories=None, cat_columns=None):
    ohe_categories = 'auto'
    if categories and len(categories) > 0:
        ohe_categories = categories
    ohe = OneHotEncoder(handle_unknown='ignore', categories=ohe_categories)

When categories is None, it works fine. But if I pass something, I get an error:

ValueError: The truth value of a Index is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

I am calling the function with:

training_x, training_y, categories, cat_columns = loader.load_data(
    'data/training.csv')

test_x, test_y = loader.load_data(
    'data/test.csv', categories=categories, cat_columns=cat_columns)

How can I check properly?

Some values aren't considered Truthy just because they exist (or have something in it). You are passing an Index which does not behave like you expect for if categories.... Try if categories != None and ... — Error - Syntactical Remorse
– Error - Syntactical Remorse, Commented Jun 28, 2019 at 15:31

Code-Apprentice · Accepted Answer · 2019-06-28 15:35:05Z

7

You are passing a value which doesn't support conversion to a bool. In this case, you need to explicitly check if the value is not None:

if categories is not None:

answered Jun 28, 2019 at 15:35

Code-Apprentice

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Comments

dallonsi · Accepted Answer · 2019-06-28 15:33:58Z

7

I suggest this:

def load_data(datafile, categories=None, cat_columns=None):
    ohe_categories = 'auto'
    if categories is not None:
        if len(categories) > 0:
            ohe_categories = categories
    ohe = OneHotEncoder(handle_unknown='ignore', categories=ohe_categories)

answered Jun 28, 2019 at 15:33

dallonsi

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