keyword 'in' not returning a bool?

[c james]

Try this
False

Why is this? Now tryTrue

Can someone explain what is going on?

 

[Larry Bates]

Try this

False

Why is this? Now try
True

Can someone explain what is going on?

Precedence. In:

't' in sample == True

sample == True is evaluated first
then 't' in that which is false

you should write

('t' in sample) == True

but that is unnecessary because

t' in sample

is easier to read and to code and less prone to this problem.

-Larry

 

[Richard Brodie]

False

It's comparison operator chaining:

't' in sample == True is like 't' == sample == True

and is equivalent to 't' in sample and sample == True

 

[Arnaud Delobelle]

Try this


False

Why is this?  Now try>>> bool('t' in sample) == True

True

Can someone explain what is going on?

This is because in Python '==' and 'in' are comparison operators and
in Python you can chain comparisons.

Typical usage is:

if 3 <= x < 9: # meaning (3 <= x) and (x < 9)
# do something...

So 't' in sample == True means the same as

('t' in sample) and (sample == True)

Which will never be true as sample is a dictionary.

To solve this, use brackets:
True

HTH

 

[Sion Arrowsmith]

False

Why is this?

http://docs.python.org/lib/comparisons.html

"Comparisons can be chained arbitrarily; for example, x < y <= z is
equivalent to x < y and y <= z, except that y is evaluated only once
[ ... ]
Two more operations with the same syntactic priority, "in" and "not
in", are supported only by sequence types"

So:
't' in sample == True
is equivalent to:
't' in sample and sample == True
and obviously:False