How to iterate through pandas columns?

I have a df that looks like this:

measurement_3      329
measurement_4      409
measurement_5      508
measurement_6      624
measurement_7      720
measurement_8      846
measurement_9      904
measurement_10    1067
measurement_11    1136
measurement_12    1240
measurement_13    1303
measurement_14    1440
measurement_15    1542
measurement_16    1678
measurement_17    1740

How do I iterate through the column names so that I can get the mean of each column without manually doing it?

I have done the following, but would like a more optimised solution using a for loop:

# Mean
dataset['loading'].fillna(dataset['loading'].mean(), inplace=True)

# Mean + std

dataset['measurement_3'].fillna(dataset['measurement_3'].mean() + dataset['measurement_3'].std(), inplace=True)
dataset['measurement_4'].fillna(dataset['measurement_4'].mean() + dataset['measurement_4'].std(), inplace=True)
dataset['measurement_5'].fillna(dataset['measurement_5'].mean() + dataset['measurement_5'].std(), inplace=True)
# continues to measurement_17