Choose largest odd number python

Question

I am trying to make a simple program in Python that calculates the largest odd number out of the values x, y, z. How do I give the user an option to pick the values for x, y, and z?

So the program will ask what x, y, and z is and then say "x,y,z is the largest odd" or the numbers are all even.

What I have so far is below. Is this at least a decent start?

  # This program exmamines variables x, y, and z 
  # and prints the largest odd number among them

  if x%2 !== 0 and x > y and y > z:
      print 'x is the largest odd among x, y, and z'
  elif y%2 !== 0 and y > z and z > x:
     print 'y is the largest odd among x, y, and z'
  elif z%2 !== 0 and z > y and y > x:
     print 'z is the largest odd among x, y, and z'
  elif x%2 == 0 or y%2 == 0 or z%2 == 0:
     print 'even'

With thkang post, I now have:

  # This program exmamines variables x, y, and z 
  # and prints the largest odd number among them

  if x%2 !== 0:
    if y%2 !== 0:
      if z%2 !== 0:
        if x > y and x > z: #x is the biggest odd
        elif y > z and y > x: #y is the biggest odd
        elif z > x and z > y: #z is the biggest odd

      else: #z is even
        if x > y: #x is the biggest odd
        else: #y is the biggest odd

    else: #y is even
      if z%2 != 0: #z is odd
        if x > z: #x is the biggest odd
        else: #z is the biggest odd
      else: #y,z are even and x is the biggest odd

  else: #x is even
    if y%2 != 0 and z%2 != 0; #y,z is odd
      if y > z: #y is the biggest odd
      else: #z is the biggest odd
    else: #x and y is even
      if z%2 != 0: #z is the biggest odd

Answer 1

Approach

Avoid using if-stmts to find maximum. Use python builtin max. Use either generator or filter to find only the odd numbers.

Using builtins like this is safer/more reliable because it is simpler to compose them, the code is well-tested, and the code executes mostly in C (rather than multiple byte code instructions).

Code

def find_largest_odd(*args):
    return max(arg for arg in args if arg & 1)

or:

def find_largest_odd(*args):
    return max(filter(lambda x: x & 1, args))

Test

>>> def find_largest_odd(*args):
...     return max(arg for arg in args if arg & 1)
... 
>>> print find_largest_odd(1, 3, 5, 7)
7
>>> print find_largest_odd(1, 2, 4, 6)
1

and:

>>> def find_largest_odd(*args):
...     return max(filter(lambda x: x & 1, args))
>>> print find_largest_odd(1, 3, 5, 7)
7
>>> print find_largest_odd(1, 2, 4, 6)
1

If you pass an empty sequence or provide only even numbers, you will get a ValueError:

>>> find_largest_odd(0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in find_largest_odd
ValueError: max() arg is an empty sequence

References

• filter
• max
• generators