add column to df from another df

#using the insert function:
df.insert(location, column_name, list_of_values) 
#example
df.insert(0, 'new_column', ['a','b','c'])
#explanation:
#put "new_column" as first column of the dataframe
#and puts 'a','b' and 'c' as values

#using array-like access:
df['new_column_name'] = value

#df stands for dataframe

Here is what the above code is Doing:
1. Create a new column called ‘new_column_name’
2. Set the values of the new column to be equal to ‘value’

Note that ‘value’ can be a list, a Series, or a scalar value.