Assigning Lambda Expression to a Variable-CodePudding

I want to include a variable to a lambda function. I want to replace sales with a variable that I can assign at the beginning of my script so that I don't have to search for this lambda function deep in my code everytime I want to change the metric being measured.

This is the current approach without assigning a variable.

df = (df_raw.rename(columns = {"col1" : "col2", "col3":"col4"})
             .assign(day = lambda x: pd.to_datetime(x.day),
                     orders = lambda x: x.sales.astype(int)

When I try assigning sales to a variable it does not work.

metric = "sales"
kpi = ("lambda x: x."   metric   ".astype(int)")

df = (df_raw.rename(columns = {"col1" : "col2", "col3":"col4"})
             .assign(day = lambda x: pd.to_datetime(x.day),
                     orders = kpi

Is there a better way of doing this? This provides an error when attempting this

CodePudding user response：

You are not defining a lambda function, but a simple string. This won't lead to execution of a function but assignment of the literal string.

Use:

metric = "sales"
kpi = lambda x: x[metric].astype(int)