创建一个带有未定义数量参数的定义

Question

What would be the best method of turning a code like below to be able to accept as many dataframes as we would like?

def q_grab(df, df2, df3, q): #accepts three dataframes and a column name. Looks up column in all dataframes and combine to one
    data = df[q], df2[q], df3[q]
    headers = [q+"_1", q+"_2", q+"_3"]
    data2 = pd.concat(data, axis = 1, keys=headers)
    return data2

q = 'covid_condition'
data2 = q_grab(df, df2, df3, q) #If I run function pid_set first, it will create new df based on pID it looks like

Answer 1

One approach is to use * operator to get a list of arguments (but name your final argument, so it isn't part of the list):

Something like this:

def q_grab(*dfs, q=None): # q is a named argument to signal end of positional arguments
    data = [df[q] for df in dfs]
    headers = [q+"_"+str(i) for i in range(len(dfs))]
    data2 = pd.concat(data, axis = 1, keys=headers)
    return data2

q = 'covid_condition'
data2 = q_grab(df, df2, df3, q=q)    

A probably cleaner alternative, is to go ahead and pass a list of dataframes as the first argument:

 def q_grab(dfs,q):
   

called with:

 data2 = q.grab([df,df2,df3], q)

using the function code as above