Finding minimum, maximum value of a list in Python [duplicate]

Question

I'm writing a program that, via a while loop, takes user-entered data and adds each value to a list (they're temperatures) until the user enters 'q' (quit). I need to find the minimum and maximum value of the list. Here is my code so far:

temps = []
daily = 1

daily = float(daily)
while daily != "q":
    daily = (raw_input("Today's Temperature: "))
    if str.isdigit(daily) and daily>0:
        temps.append(daily)
    elif daily<0:
        print "Positive temperatures only please."
else: 
    print "Calculating statistics..."

temps = sorted(temps)
print map(float, temps)

maximum = (max(temps))
print "Maximum:",maximum

When I run this and enter values (90, 80, 70, 60, 50, q) it works fine and gives me 90 as the maximum and 50 as the minimum.

However, when I run this and enter values (30, 28, 1, 9, 26, 14, q) it returns 9 as the maximum and 1 as the minimum.

Basically, it treats 9.0 as greater than any number that starts with 8 or less. (i.e. 88, 56, 30, etc.)

How do I fix that?

Did not read the code yet, but you are probably comparing strings, not numbers. Yep, all those temperatures are strings. Use int or double to turn them into actual numbers. — tobias_k
– tobias_k, Commented Feb 27, 2015 at 15:42
If any of the answers solved your problem, please consider accepting an answer to mark the question as being resolved. — tobias_k
– tobias_k, Commented Mar 9, 2015 at 13:35

tobias_k · Accepted Answer · 2015-02-27 15:52:23Z

2

You are never converting daily to a float inside your loop, thus all those values in the lists are strings. And as a string, "9" is larger than "30". Similarly, your comparison daily>0 does not work as expected, as you are comparing strings with numbers; this condition will always be true -- except in Python 3, where it will rightfully raise an exception.

I suggest you try something like this:

while True:
    daily = raw_input("Today's Temperature: ")
    if daily == "q":
        break
    elif daily.isdigit() and float(daily) > 0:
        temps.append(float(daily))
    else:
        print "Positive numeric temperatures only please."

answered Feb 27, 2015 at 15:52

tobias_k

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Comments

rxmxn · Accepted Answer · 2015-02-27 17:20:54Z

1

I made some changes in your code so you compare float numbers instead of strings. I also used sort instead of mapping (but it was just to show you another way).

temps = []

while True:
    daily = raw_input("Today's Temperature: ")
    if daily == 'q':
        break
    elif daily.isdigit():
        daily = float(daily)  # after this you can do whatever you want with daily as a number
        if daily > 0:
            temps.append(daily)
        elif daily == 0:
            print "Temperature 0 is not allowed."
    else:
        print "Only possitive numbers for temperature please."


temps.sort()
print temps[0]  # returning the minimum value
print temps[-1]  # returning the maximum value

You can also use heaps (if you want to assure a logarithmic running time):

import heapq

heapq.heapify(temps)
print heapq.nsmallest(1, temps)
print heapq.nlargest(1, temps)

edited Feb 27, 2015 at 17:20

answered Feb 27, 2015 at 16:04

rxmxn

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3 Comments

mbomb007 Over a year ago

And the print() function is different in Python 3.

smassey Over a year ago

@xRa I would recommend your reverse your daily != 'q' to say: if daily == 'q': break and not use an else to have less indentation (easier to read once the blocks of conditional code grow larger than just a couple lines).

tobias_k Over a year ago

What happens if daily == 0?

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