Python's Most Efficient Way to Choose Longest String in List

Python's most efficient way to choose longest string in list?

From the Python documentation itself, you can use max:

>>> mylist = ['123','123456','1234']
>>> print max(mylist, key=len)
123456

Longest string from a tuple in a list

You can use a dictionary (defaultdict) to keep track of the longest message per ID:

from collections import defaultdict

# input
l = [("Hello world","1"), ("Helloworld","2"),("Hi, Hello world","1"),("How are you","3"),("HiHelloworld","2")]

d = defaultdict(lambda:('', float('-inf')))
for msg, ID in l:
    if len(msg) > len(d[ID][0]):
        d[ID] = (msg, ID)
out = list(d.values())

output:

[('Hi, Hello world', '1'), ('HiHelloworld', '2'), ('How are you', '3')]

Get the longest string from the list using python

You can fin the longest and the shortest strings in the list the following way:

a_list = ['abc', 'bcd', 'bcdefg', 'abba', 'cddc', 'opq']

# we give the both variable the value of the first element in the list 
shortest = a_list[0]  
longest = a_list[0]  

for i in a_list[1:]:
    if len(shortest) >= len(i):  # check if current string in shorter 
        shortest = i # if yes change variable value

    if len(longest) <= len(i):  # check if current string in longer
        longest = i # if yes change variable value

# print results:
print(shortest)
print(longest)

Most Pythonic and efficient to join list of strings until the length gets too high

products = ["Apple", "Banana", "Cherry", "Durian"]

string = products[0]

for v in products[1:]:
    if len(string) + len(', ') + len(v) <= 20:
        string = string + ', ' + v
    else:
        string = string + '...'
        break

print(string)

Output:

Apple, Banana...

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

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

Longest strings from list

First, we can find the maximum length of any string in the list:

stringlist = ['hi', 'hello', 'hey','ohman', 'yoloo', 'hello']
#maxlength = max([len(s) for s in stringlist])
maxlength = max(len(s) for s in stringlist)  # omitting the brackets causes max 
                                             # to operate on an iterable, instead
                                             # of first constructing a full list
                                             # in memory, which is more efficient

A little explanation. This is called a list comprehension, which allows you to comprehend one list as another list. The code [len(s) for s in stringlist] means "generate a list-like object, by taking stringlist, and for every s in that list, give me instead, len(s) (the length of that string).

So now we have a list [2, 5, 3, 5, 5, 5]. Then we call the built-in max() function on that, which will return 5.

Now that you have the max length, you can filter the original list:

longest_strings = [s for s in stringlist if len(s) == maxlength]

This does just as it reads in english: "For each string s in stringlist, give me that string s, if len(s) is equal to maxlength."

Finally, if you want to make the result unique, you can use the set() constuctor to generate a unique set:

unique_longest_strings = list(set(longest_strings))

(We are calling list() to turn it back into a list after removing the duplicates.)

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This boils down to:

ml = max(len(s) for s in stringlist)
result = list(set(s for s in stringlist if len(s) == ml))

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Note: Don't use a variable named list, as it overrides the meaning of the name for the list type.

print the length of the longest string in the list

names = ['ron', 'james', 'kevin07']

best = 0

for index in range(len(names)):
    if len(names[index]) > best:
        best = len(names[index])

print(best)

Output:

7

Explanation:

You need to move the print(best) outside of loop

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