Python | Extract length of longest string in list
Last Updated :
17 Apr, 2023
Sometimes, while working with a lot of data, we can have a problem in which we need to extract the maximum length of all the strings in list. This kind of problem can have application in many domains. Let’s discuss certain ways in which this task can be performed.
Method #1 : Using max() + generator expression, The combination of above functionalities can be used to perform this task. In this, we extract all the list lengths using generator expression and return maximum of them using max().
Python3
test_list = [ 'gfg' , 'is' , 'best' ]
print ("The original list : " + str (test_list))
res = max ( len (ele) for ele in test_list)
print ("Length of maximum string is : " + str (res))
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Output :
The original list : ['gfg', 'is', 'best']
Length of maximum string is : 4
Time Complexity: O(n), where n is the length of the input list. This is because we’re using max() + generator expression which has a time complexity of O(n) in the worst case.
Auxiliary Space: O(1), as we’re using constant additional space.
Method #2 : Using len() + key argument + max() The combination of above functions can be used to perform this task. In this, we extract the maximum length using len() and max(). It is faster than above method as it performs more task built in rather than overhead by generator expression.
Python3
test_list = [ 'gfg' , 'is' , 'best' ]
print ("The original list : " + str (test_list))
res = len ( max (test_list, key = len ))
print ("Length of maximum string is : " + str (res))
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Output :
The original list : ['gfg', 'is', 'best']
Length of maximum string is : 4
Time Complexity: O(n), where n is the length of the list test_list
Auxiliary Space: O(1) constant additional space required
Method 3: Alternative method
Python3
lst = [ 'gfg' , 'is' , 'best' ]
max_length,longest_element = max ([( len (x),x) for x in (lst)])
print ( "max length is: " ,max_length)
print ( "longest string is: " , longest_element)
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Output
max length is: 4
longest string is: best
Method 4: Using the enumerate function
Python3
lst = [ 'gfg' , 'is' , 'best' ]
max_length,longest_element = max ([( len (x),x) for a,x in enumerate (lst)])
print ( "max length is: " ,max_length)
print ( "longest string is: " , longest_element)
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Output
max length is: 4
longest string is: best
Method 5: Using the reduce function
One unique approach to extract the maximum length of all strings in a list is using the built-in function “reduce” from the “functools” module. The reduce function applies a function cumulatively to the elements of an iterable and returns a single output. In this case, we can use the function “max” as the cumulative function and the iterable is a list of the lengths of each string in the original list.
Here is an example of how to use the reduce function to extract the maximum length of all strings in a list:
Python3
from functools import reduce
test_list = [ 'gfg' , 'is' , 'best' ]
res = reduce ( lambda x, y: max (x, y), map ( len , test_list))
print ( "Length of maximum string is : " + str (res))
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Output
Length of maximum string is : 4
Time complexity: O(n)
Auxiliary Space: O(n)
Method 6: Using the list comprehension:
Python3
test_list = [ 'gfg' , 'is' , 'best' ]
string_lengths = [ len (i) for i in test_list]
max_length = max (string_lengths)
print ( "Length of maximum string is :" , max_length)
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Output
Length of maximum string is : 4
Time complexity: O(n)
Auxiliary Space: O(n)
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