How to find the longest string in a list of lists of strings?

user_6906586 0
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How to find the longest string in a list?

This list has both strings and list of strings.

a set of strings, but the weirdness comes in that the strings I'm checking are in lists and those lists are mixed in with strings in a larger list.

Example value for 'entries':

extries = [["this is text", "more text"], "another string"]

python code

length = 0
for i in entries:
        if(type(i) is list):
            for x in i:
                x = str(x)
            if length << len(max(i, key = len)):
                length = len(max(i, key = len))
        else:
            for i in entries:
                i = str(i)
                if length << len(i):
                    length = len(i)

This should make

length = len(max(["this is text","more text","another string"])

but it is making length = 0.

python-3.x list python string
3 Answers

The following code will give you the length of the largest string -- whether or not it is inside a subset. 

entries = [["this is text", "more text"], "another string"]

length = 0
for i in entries:
    if type(i) is list:
        value = len(max(i, key=len))
        if length < value:
            length = value
    else:
        value = len(i)
        if length < value:
            length = value

print(len("this is text"), len("more text"), len("another string"))
print(length)

Outputs:

12 9 14
14
user_13054610

I'd break the code down in two, first have a function that flattens an arbitrarily deep list:

def flatten(lst, ret):
    for x in lst:
        if type(x) == list:
            flatten(x, ret)
        else:
            ret.append(x)

Then just use it with your input and an empty list to get a flattened list out, and call max:

temp = []
entries = [["this is text", "more text"], "another string"]
flatten(entries, temp)
max(temp, key=len)

Notice that this would also work with an input like this entries = [[["this is text", "more text"]], ["another string"], "the longest string of them all"].

user_120624040

For arbitrary deep nested lists, I would first make a list flattening function:

def flatten_nested_list(lst):
    for item in lst:
        if isinstance(item, list):
            yield from flatten_nested_list(item)
        else:
            yield item

Then you can call max() with key=len to get the longest word:

print(max(flatten_nested_list(entries), key=len))
# another string
user_52389150
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