How to pass a function as a parameter to another function? - python-3.x

Question

I'm doing a bunch of operations on pandas dataframes. For example finding max, min and average inside columns and return the column names in a new column. Now I'm trying to wrap these things into a function, and use max() and/or min() as arguments in this function.
Below is a snippet that describes what I'm trying to do in a very simplified way. In its current state it also returns a description of the desired output. The snippet does not have the desired functionality and flexibility though.
The setup:
# Sample dataframe
df = pd.DataFrame({'col_A':[1,20,6,1,3]})
def findValue(function, df, colname):
print(function) # just a placeholder
df[colname] = df.max()[0]
return df
df2 = findValue(function='max', df=df, colname='col_B')
print(df)
Output 1:
col_A col_B
0 1 20
1 20 20
2 6 20
3 1 20
4 3 20
A naive attempt:
# Sample dataframe
df = pd.DataFrame({'col_A':[1,20,6,1,3]})
# The function I would like to use in another function is max()
# My function
def findValue(function, df, colname):
df[colname] = df.function()[0]
return df
df2 = findValue(function=max(), df=df , colname='col_B')
print(df)
Output 2:
Traceback (most recent call last):
File "<ipython-input-7-85964ff29e69>", line 1, in <module>
df2 = findValue(function=max(), df=df , colname='col_B')
TypeError: max expected 1 arguments, got 0
How can I change the above snippet so that I can change function = max() to function = min() or any other function in the arguments of findValue()? Or even define a list of functions to be used in a similar manner?
Thank you for any suggestions!

Answer 1

You are very, very close. You pretty much just need to remove the parens when passing in the function. Here's a simplified example that loops over a list of function names, and appears to do what you want:
def findValue(func, x, y):
return func(x, y)
for calc in (max, min):
result = findValue(func=calc, x=1, y=10)
print(result)
Output:
10
1