and/or in Lists

[Bushido]

Hello everyone!

Please advise why it does not works

test=['a', 'b', 'c', 'd', 'h']
if 'a' and 'b' in test:
    print ('everything is ok')
else:
    print ('something went wrong')

Result is "everything is ok"

But when i use Or statement:

test2=['a', 'b', 'c', 'd', 'h']
if 'i' or 'j' in test2:
    print ('everything is ok')
else:
    print ('something went wrong')

Result is "everything is ok" as well.

[buran]

https://python-forum.io/Thread-Multiple-...or-keyword

test=['a', 'b', 'c', 'd', 'h']
if 'a' in test and 'b' in test:
    print ('everything is ok')
else:
    print ('something went wrong')

same for or

you may want to look also at all() and any() built-in functions

[harsimarriar96]

It does not work like english, You need to check each condition specifically.

if ('a' in test) and ('b' in test)

[volcano63]

You were shown the proper form; let me provide you with an explanation.

In Python any non-empty value evaluates to True in boolean expressions, and empty - empty list, empty dict, empty string, etc - to False. Also, 0 and None are False equivalent, and non-zero value is True

But there's an interesting Python peculiarity - a composite boolean expression takes the value of the last expression that defines whether the final result is True or False

Output:
In [10]: test=['a', 'b', 'c', 'd', 'h']

In [11]: 'a' and 'b' in test
Out[11]: True

In [12]: 'i' or 'j' in test
Out[12]: 'i'

In [13]: 'b' in test and 'a'
Out[13]: 'a'

In [14]: 'a' and True
Out[14]: True

In [15]: True and 'a'
Out[15]: 'a'

In [16]: 'a' and 0
Out[16]: 0

In [17]: False and 'a'
Out[17]: False

In [18]: 'a' or False
Out[18]: 'a'

In [19]: True or 'a'
Out[19]: True

In [20]: '' and False
Out[20]: ''

Occasionally this is used as a replacement for ternary operation

Output:
In [21]: x = 1

In [22]: 'a' if x == 2 else 'b'
Out[22]: 'b'

In [23]: x == 2 and 'a' or 'b'
Out[23]: 'b'

There are couple of shortcomings for the latter technique

• You have to be very careful about the order of operands
  
• Ternary operations are faster
  
• You may be chased by a mob of purists with pitchforks and torches