Conditional assignments
I was wondering, is it possible to do something like the following? The given code obviously doesn't work.
l = 5
(l == 5)*(k = 7) #Returns error message.
The reason is, I'd rather avoid doing something like the following for the project I'm currently working on.
if stmt1 == True or stmt2 == True:
if stmt1 == True:
k = 7
if k == 7:
# Evaluate suite
else:
# Evaluate different suite
Related Article: 3 way conditional loop?
is a Python discussion thread by Yoink that has 3 replies, was last updated 1 year ago and has been tagged with the keywords: multi, way, continditional, boolean, loop.
Thisisnotanid
Junior Poster in Training
60 posts since Dec 2010
Reputation Points: 10
Solved Threads: 0
Skill Endorsements: 0
No it's not possible to have assignments in if conditions. The reason is that assignment is a statement and cannot be part of an expression (the same applies to += -=, etc), while the 'if' statement expects an expression. The potential problem with your code above is that it evaluates stmt1 several times. You could write it this way
c = expr1
if c or expr2:
if c:
k = 7
if k == 7:
# etc
else:
# etc
Notice that '== True' is usually not needed. I know it looks restricting if you're used to C code, but it is one of the features that make python code clear.
Gribouillis
Posting Maven
3,101 posts since Jul 2008
Reputation Points: 1,130
Solved Threads: 761
Skill Endorsements: 11
Something along these lines?
>>> ctrl = 5
>>> k = 7 if ctrl == 5 else None
>>> k
7
pyTony
pyMod
6,305 posts since Apr 2010
Reputation Points: 879
Solved Threads: 986
Skill Endorsements: 26
Thanks fellas, that was helpful. Gribouillis, It turns out that the method you outlined is actually equivalent to what I am trying to do, so I can make use of that. PyTony, I wanted to have the assignment nested in an if statement; I was hoping to avoid having to do precisely what you outlined.
Thisisnotanid
Junior Poster in Training
60 posts since Dec 2010
Reputation Points: 10
Solved Threads: 0
Skill Endorsements: 0
Question Answered as of 1 Year Ago by
Gribouillis
and
pyTony It turns out that something like what's being discussed is possible. It's not equivalent, but if you design with this catch in mind, you can make your programs behave in a way which mimics the desired behavior:
l = 5
k = 7*(l == 5)
Note, that while implementing boolean algebra in such a way can come handy, it can not always replace logic. For example, if '*' in the following is not replaced with 'and', the code will return an error message.
list = range(10) # Some list
a = len(list)
b = a + 5
for l in xrange(b):
if (l < a)*(not list[l]%2):
print list[l]
Thisisnotanid
Junior Poster in Training
60 posts since Dec 2010
Reputation Points: 10
Solved Threads: 0
Skill Endorsements: 0