I'm not sure if I understand it wrong or if the codes below are wrong but from my understanding the following codes should give the same output:

transactions[transactions['date'].str[14:16] == '21' | transactions['date'].str[14:16] == '22']

and

transactions.query("date.str.slice(11, 13) == '21' | date.str.slice(11, 13) == '22'")

I get an error when I try the first code:

transactions[transactions['date'].str[14:16] == '21' | transactions['date'].str[14:16] == '22']

error:

TypeError: Cannot perform 'ror_' with a dtyped [object] array and scalar of type [bool]

But when using .query method i get no errors:

transactions.query("date.str.slice(11, 13) == '21' | date.str.slice(11, 13) == '22'")

How can i change the first code without using the query method and getting the same output as the second code with the query method?

CodePudding user response：

This is because of Python's operator precedence. | is more important than ==, so '21' | transactions['date'].str[14:16] gets evaluated before transactions['date'].str[14:16] == '21'.

To fix the first line of code, simply add parentheses around the == conditions:

transactions[(transactions['date'].str[14:16] == '21') | (transactions['date'].str[14:16] == '22')]

Or, if you prefer, use .eq instead of ==:

transactions[transactions['date'].str[14:16].eq('21') | transactions['date'].str[14:16].eq('22')]