If Else Statements , AND OR logic operations, and text files (using Python) [duplicate]

Question

I'm having some trouble with AND and OR within if else statements. This is my code:

if subject == 'history' or subject == 'History' and unit == 'WWII' or unit == 'ww2':

Any ideas how to fix this?

coding hint: userName, subject, unit, score, grade = hisWw2[:5] — grovina
– grovina, Commented Dec 31, 2017 at 15:40
At first you should use parentheses to group the logical operators (and, or). The may not always be necessary but in complex expressions they are helpful to understand the expression — Michael Butscher
– Michael Butscher, Commented Dec 31, 2017 at 15:40
all operators have a "weight" and "assosiativity" - they bind differently strong. Use ( ) to reformulate your logical assumptions so they bind in a way that fits. FALSE and TRUE or FALSE is always FALSE bexause and binds stronger then or does .... use () -- weight is the wrong word - brb - see answer for doku on pythons operators. — Patrick Artner
– Patrick Artner, Commented Dec 31, 2017 at 15:42
Yep the brackets are working thanks! I never knew you could put brackets around logic operators. — qwe
– qwe, Commented Dec 31, 2017 at 15:48

Patrick Artner · Accepted Answer · 2017-12-31 15:53:20Z

Read up on operator-precedence - some operators bind stronnger then others - to get your desired logical output you should use ( ) to structure your logical conditions.

Summarization:

Operator                              Description
lambda                                Lambda expression
if – else                             Conditional expression
or                                    Boolean OR
and                                   Boolean AND
not x                                 Boolean NOT
in, not in, is, is not, <, <=, >, >=, !=, ==  Comparisons, including membership tests and identity tests
|                                     Bitwise OR
^                                     Bitwise XOR
&                                     Bitwise AND
<<, >>                                Shifts
+, -                                  Addition and subtraction
*, @, /, //, %                        Multiplication, matrix multiplication, division, floor division, remainder [5]
+x, -x, ~x                            Positive, negative, bitwise NOT
**                                    Exponentiation [6]
await x                               Await expression
x[index], x[index:index], x(arguments...), x.attribute       Subscription, slicing, call, attribute reference
(expressions...), [expressions...], {key: value...}, {expressions...}     Binding or tuple display, list display, dictionary display, set display

The ealier the operator the higher it binds. Please see the linked doku for subscription context

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