# Creating a function that calculate the mean with out using a built in function on python

Hi I am trying to create a function that will calculate the mean of a column in a dataframe, without using python built in functions.
This is how I did it initially

``````    A       B
0   180.0   70
1   170.0   65
2   190.5   80
3   175.0   75
4   190.0   90
5   190.0   90
6   195.0   95
7   200.0   100
8   205.0   105
9   210.0   110
``````
``````n =len(df2["B"])
total = sum(df2["B"])
mean=total/n
``````

Now I wanted to create a built in function this was my attempt but it is giving me an error. Please assist where I went wrong. (A disclaimer this is a tutorial question).

``````def summary_statistics(df, column_name):
n =len(df2[column_name])
total=sum(df2[column_name])
mean = total/n
return mean

summary_statistics(df2,["B"])
``````

### >Solution :

You need to do this:

``````def summary_statistics(df, column_name):
n =len(df[column_name])
total=sum(df[column_name])
mean = total/n
return mean

summary_statistics(df2, "B")
``````