Lambda with nested if else is not working

Question

I'm newbie to Python and am learning lambda expressions at the moment. I was solving a tutorial program

Define a function max_of_three() that takes three numbers as arguments and returns the largest of them.

I've gone through this old post and tried without success:

>>> max_of_three = lambda x, y, z : x if x > y else (y if y>z  else z)
>>> max_of_three(91,2,322)
91

Why it's not returning Z? It's X.

Look at your logic closely. X is bigger than Y, so it returns X. — Morgan Thrapp, Jul 08 '15 at 13:25
Elaborating on what Morgan explained: It never gets to your else... — Jacques de Hooge, Jul 08 '15 at 13:27
Not the problem with your function, but there is a builtin `max` function you could use: `max_of_three = lambda x, y, z : max(x,y,z)` — Holloway, Jul 08 '15 at 13:29
max (x, y, z) or something like x if x > y and x > z else y if y > z else z — Jacques de Hooge, Jul 08 '15 at 13:29
@VigneshKalai, it didn't really answer the question of why the original code didn't work. Bruce has now answered with the same thing. — Holloway, Jul 08 '15 at 13:31
@Trengot it is always acceptable if you provide a method better then the OP's but never mind it has been answered — The6thSense, Jul 08 '15 at 13:33
@Trengot : I've seen your comment /after/ posting mine, kudos for being first one :-) — Bruce, Jul 08 '15 at 13:34

ZdaR · Accepted Answer · 2015-07-08T13:28:21.167

8

Currently you are using if x > y which only compares the x and y, but you need to compare the x with z as well at the same step.

max_of_three = lambda x, y, z: x if x > y and x > z else (y if y > z else z)
print max_of_three(91, 2, 322)
>>> 322

edited Jul 08 '15 at 13:28

answered Jul 08 '15 at 13:26

ZdaR

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score 5 · Answer 2 · answered Jul 08 '15 at 13:29

5

or, make it simpler:

max_of_three=lambda x,y,z:max((x,y,z))

max_of_three(1,2,3)
3

I know it's cheating, but using the language primitives is usually easier :-)

answered Jul 08 '15 at 13:29

Bruce

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One of the great advantages of python is that it has countless libraries and functions for _almost_ every problem. Hence, i'd rather read documentation such as numpy or scipy and apply it to my problem than starting from scratch. (in short: +1) – Daniel Lenz Jul 08 '15 at 13:33

Cleb · Answer 3 · 2015-07-08T13:36:07.223

2

You can modify your function as follows:

max_of_three = lambda x, y, z : x if x > y and x > z else (y if y>z  else z)

Your problem was that you did not check, whether x is also larger than z. In your case x is larger than y, therefore, it just returns x and does not compare it to z anymore.

edited Jul 08 '15 at 13:36

answered Jul 08 '15 at 13:27

Cleb

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Lambda with nested if else is not working

3 Answers3