How to replace part of a function call with variable in Python?

Question

I have a dictionary with some function expressions as values. Each of the values are very similar, except the part in the middle. In the following example, only earn_yld, free_cash_flow_yield and eps_growth are different in the long formula.

factor_bql = {
    "ltm_earnings_yield": bq.func.dropna(bq.data.earn_yld(as_of_date=bq.func.RANGE(params['start'],params['end']))),
    "ltm_fcf_yield": bq.func.dropna(bq.data.free_cash_flow_yield(as_of_date=bq.func.RANGE(params['start'],params['end']))),
    'ltm_eps_growth': bq.func.dropna(bq.data.eps_growth(as_of_date=bq.func.RANGE(params['start'],params['end'])))
}

Is there any way to write a function or variable to simplify the values of the dictionary to something like

def simple_formula(xyz):
    ... ...

factor_bql = {
    "ltm_earnings_yield": simple_formula('earn_yld'),
    "ltm_fcf_yield": simple_formula('free_cash_flow_yield'),
    'ltm_eps_growth': simple_formula('eps_growth')
}

Tupteq · Accepted Answer · 2020-03-30 21:02:04Z

1

I'd do this in following way:

def simple_formula(fn):
    return bq.func.dropna(fn(as_of_date=bq.func.RANGE(params['start'],params['end'])))

factor_bql = {
    "ltm_earnings_yield": simple_formula(bq.data.earn_yld),
    "ltm_fcf_yield": simple_formula(bq.data.free_cash_flow_yield),
    'ltm_eps_growth': simple_formula(bq.data.eps_growth)
}

So, functions themselves (not their names) are parameters of simple_formula.

edited Mar 30, 2020 at 21:02

answered Mar 30, 2020 at 18:47

Tupteq

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2 Comments

DarrylG Over a year ago

@Tupteq--I suppose argument xyz is superfluous in simpe_formula?

Tupteq Over a year ago

@DarrylG I assumed xyz to represent an example parameter (as in question). But I think you're right, I'll remove it.

Ewaren · Accepted Answer · 2020-03-30 18:48:33Z

0

You can use the globals function to call a function in the current module by the string representation of its name.

def func1(bar):
    return "func1" + str(bar)


def func2(bar):
    return "func2" + str(bar)


def simple_formula(func_name):
    return globals()[func_name](bar="baz")


factor_bql = {
    "key1": simple_formula("func1"),
    "key2": simple_formula("func2"),
}

print(factor_bql["key2"]) # prints "func2baz"

answered Mar 30, 2020 at 18:48

Ewaren

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Comments

Błotosmętek · Accepted Answer · 2020-03-30 19:06:51Z

0

Assuming bq.data is some object:

def simple_formula(xyz):
    method = getattr(bq.data, xyx) # get a method by its name
    return bq.func.dropna(method(as_of_date=bq.func.RANGE(params['start'],params['end'])))

edited Mar 30, 2020 at 19:06

answered Mar 30, 2020 at 18:44

Błotosmętek

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2 Comments

Leon Over a year ago

Thanks. I tried that approach and got the following error message: ``` File "<ipython-input-32-40f549057bae>", line 20 return bq.func.dropna(method((as_of_date=bq.func.RANGE(params['start'],params['end']))) ^ SyntaxError: invalid syntax ``` Looks like that the equal sign in the formula is generating syntax error. That is not the issue if I directly use the formula, rather than simple_formula function.

Tupteq Over a year ago

Looks like brackets don't match.

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