Python - Defining a variable without initializing, but with a value

Question

I'm working on a small task from the checkio-python coding game. It involves hard-scripting the built-in functions min() and max().

Anyway to "store" the minimal or maximal value, I thought of initializing a variable first and then store the respective lowest or highest value in it.

min_value = None

...function to compare element 1 with element 2 of a list and find lowest..

min_value = lowest_value

...function continues

When I realized that I had forgotten to compare the min_value with the lowest_value, to make sure that I would have the "globally" lowest value (of the whole list). But when I compare it, it gives me a NoneError with the first initialized variable.

 min_value = None

...function to compare element 1 with element 2 and find lowest..
if lowest_value < min_value:
    NoneError

So how could I initialize a value without a value, which has in this case also the highest possible value, which then would change after the first comparison.

I hope, I that I was able to make my question clear.

Thanks!

jcamdr · Accepted Answer · 2017-11-03 13:17:29Z

2

Depend of the type of the value.

For a int, then use:

min_value = sys.maxsize

For a float, then use:

min_value = float('inf')

So any values will be smaller than those maximal numbers.

Alternatively, you can define the initial value with the first value of your list and iterate the list from the second value.

min_value = list[0]
for value in list[1:]:
    if value < min_value:
        min_value = value

This has the advantage to work with any type.

Even more alternatively, you can reduce a lambda expression like this:

min_value = reduce(lambda min_value, value: min_value if (min_value < value) else value, list)

edited Nov 3, 2017 at 13:17

answered Nov 3, 2017 at 10:56

jcamdr

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Morris Franken · Accepted Answer · 2017-11-03 10:57:02Z

0

Instead in initializing them as None, you can initialize them with a maximum/minimum integer value:

import sys
min_value = sys.maxsize
max_value = -sys.maxsize

answered Nov 3, 2017 at 10:57

Morris Franken

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Gronnesby · Accepted Answer · 2017-11-03 11:03:12Z

0

You just have to make sure that you are not comparing to None:

mylist = [2, 5, 3, 6, 7, 4, 8]
min_value = None
for num in mylist:
    if min_value is not None and num > min_value:
        continue
    else:
        min_value = num

print "Minimum value: {0}".format(min_value)

Produces:

Minimum value: 2

answered Nov 3, 2017 at 11:03

Gronnesby

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