How to find the maximum number in a list with numbers and strings in Python?

Question

I have a list which contains a word and three different numbers. I want to find a way to select the largest of these three numbers, but whenever I use the max function it selects the word instead. Is there any solution to this?

Part of my code goes as follows:

myList = list()
userName1 = input('What is your name?')
myList.append(userName1)
score1 = input('User 1 score 1')
myList.append(score1)
score2 = input('User 1 score 2')
myList.append(score2)
score3 = input('User 1 score 3')
myList.append(score3)

print(max(myList))

For these, I inputted my name (Daisy) and three numbers (6, 9 and 4). I hoped that the max function would select the 9, but instead it printed Daisy.

So it is actually a list of all strings, but some of the strings represent numbers. — khelwood
– khelwood, Commented Oct 29, 2015 at 12:05
max of list of String gives the longest String in the list hence the Daisy — Ankur Anand
– Ankur Anand, Commented Oct 29, 2015 at 12:10

xnx · Accepted Answer · 2015-10-29 12:20:29Z

2

input() returns a string holding the user's input. You need to convert your strings to integers (the ones that can be), so you could build a new list of these numbers and find the maximum of that one. This is a good use of the try...except clause: just ignore (pass) the exception you get if you try to convert something like 'Daisy' into a number.

In [1]: myList = ['one', 1, 'foo', '4', '5', '2']

In [2]: numbers = []

In [3]: for item in myList:
   ...:     try:
   ...:         numbers.append(int(item))
   ...:     except ValueError:
   ...:         # ignore items which aren't integers
   ...:         pass
   ...:     

In [4]: max(numbers)
Out[4]: 5

At the moment you're comparing string values, which will not give you the necessary maximum even when the string can be converted to integers (e.g. '10' is "less than" '9').

edited Oct 29, 2015 at 12:20

answered Oct 29, 2015 at 12:09

xnx

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2 Comments

Ankur Anand Over a year ago

After the String to Int cast print(max([i for i in myList if isinstance(i,int)])) is much better way

xnx Over a year ago

@AnkurAnand But OP's myList, as coded, will contain only strings: i.e. ['Daisy', '6', '9', '4'].

Alex · Accepted Answer · 2015-10-29 12:13:06Z

0

Untested suggestion to improve code as a whole:

userName1 = input('What is your name?')
scores = input('User scores, comma seperated')
print("user %s has max score %d"%(userName1, max(map(scores.split(','),int))))

answered Oct 29, 2015 at 12:13

Alex

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