If I have a DataFrame that for example is 91 rows 3 columns, and I would like to add a 4th column to it which measures the length of the data found in column 3. How can I apply this over each row please.

The following gives me 91 in each row, which isn’t what I’m looking for.

df[:colName] = length(df.Column3)

An example in python I would use the following below, which would measure the length of column3 on each row and input the number into column4.

df['Length'] = df.Column3.apply(len)

Many thanks.
ps. I have been trying to google and forum search. But the only answers I’m finding I cannot understand how to make it work, something to do with map.