Find maximum int value from list which contain both str and int python

问题

Looking to find max from the combine list as follows:

['filename1', 1696, 'filename2', 5809,....]

I have tried following:

max(['filename1', 1696, 'filename2', 5809,....])

that return me TypeError: '>' not supported between instances of 'int' and 'str'. Any suggestion would help. What I want is to find the max integer value from the list above mentioned.

回答1:

Use list comprehension with isinstance to extract the int and then use max.

Ex:

f = ['filename1', 1696, 'filename2', 5809]
print(max([i for i in f if isinstance(i, int)]))
#or generator
print(max((i for i in f if isinstance(i, int))))    #Better Option

Output:

5809
5809

回答2:

If your real data also has alternating strings and integers, like your example, you can just iterate in steps of size 2, starting with the second element:

values = ['filename1', 1696, 'filename2', 5809, ...]
max(values[1::2])
# 5809

Note that this slicing creates a new list (so depending on the size of the original list it might be very large).

回答3:

The same isinstance idea can be applied to a filter:

f = ['filename1', 1696, 'filename2', 5809]
max(filter(lambda i: isinstance(i, int), f))

Also, if you need to include more than one data type in your comparison, e.g.: floats, you can simple use a tuple to validate the the data to be compared:

max(filter(lambda i: isinstance(i, (int, float)), f))

回答4:

You can also use try...except clause.

lst = ['filename1', 1696, 'filename2', 5809]
numbers = []

for item in lst:
    try:
        numbers.append(int(item))
    except ValueError:
        pass # Ignore items which are not numbers

print(max(numbers))
# 5809

回答5:

max() expects iterable with comparable values. You should ignore string first from the list and then use max() on it.

Use list comprehension to only consider integer values

file_data = ['filename1', 1696, 'filename2', 5809,....]
max([elem for elem in file_data if isinstance(elem, int)])

If you are expecting float values as well, you can update it as:

max([elem for elem in file_data if not isinstance(elem, str)])

来源：https://stackoverflow.com/questions/50037992/find-maximum-int-value-from-list-which-contain-both-str-and-int-python