How to do a subtraction operation between two columns of a dataframe and then add the result with another column?

Question

I have this code:

dados_train = pd.read_csv('arquivo.csv', delimiter=",")
y = ((dados_train.pop('col_name1') - dados_train.pop('col_name2')) + (dados_train.pop('col_name2')

When I try to run just like this:

y = (dados_train.pop('col_name1') - dados_train.pop('col_name2')

Works!

But when I try:

y = ((dados_train.pop('col_name1') - dados_train.pop('col_name2')) + (dados_train.pop('col_name2')

Makes a mistake!

Why does this happen? Someone would know a solution?

Answer 1

When you use the pop it deletes the value of the variable, then the second time you actually use it there is no value in it

you can do so

y = (dados_train['col_name1'] - dados_train['col_name2']) + dados_train['col_name2']

if you use it in dictionary, you have the option of get, I don’t know if the dados_train is receiving a dictionary, but if I was can use it like this

y = (dados_train.get('col_name1') - dados_train.get('col_name2')) + dados_train.get('col_name2')

Answer 2

the method list pop.() remove an object from the last position of the list and return it to the user. As presented, I believe the list has only two elements.

try to access using brackets:

y = (dados_train['col_name1'] - dados_train['col_name2'] + dados_train['col_name2'])

Addendum: you forgot to close one of the pairs of parentheses. I closed it in the example, but this may be the problem in your application.