Python – Maximum String value length of Key

04 May, 2020
Sometimes, while working with Python dictionaries, we can have a problem in which we need to find the maximum length of all the string values of particular key. This problem can occur in domains of day-day programming and web development. Let’s discuss certain ways in which this task can be performed.
Examples –
Input:test_list = [{‘key1’ : “abcd”, ‘key2’ : 2}, {‘key1’ : “qwertyui”, ‘key2’ : 2}, {‘key1’ : “xcvz”, ‘key3’ : 3}, {‘key1’ : None, ‘key3’ : 4}]
Output: 8Explanation: Among all values for given key key1, qwertyui has maximum length (which is 8).
Method #1 : Using max() + len() + list comprehensionThe combination of above functions can be used to solve this problem. In this, we compute the maximum string length using max() and len(). The comparison with each is bound by list comprehension.
# Python3 code to demonstrate working of # Maximum String value length of Key# Using max() + len() + list comprehension  # initializing listtest_list = [{'Gfg' :  "abcd", 'best' : 2},              {'Gfg' :  "qwertyui", 'best' : 2},             {'Gfg' :  "xcvz", 'good' : 3},             {'Gfg' : None, 'good' : 4}]  # printing original listprint("The original list is : " + str(test_list))  # initializing Key filt_key = 'Gfg'  # Maximum String value length of Key# Using max() + len() + list comprehensiontemp = (sub[filt_key] for sub in test_list)res = max(len(ele) for ele in temp if ele is not None)  # printing result print("The maximum length key value : " + str(res)) 
The original list is : [{‘best’: 2, ‘Gfg’: ‘abcd’}, {‘best’: 2, ‘Gfg’: ‘qwertyui’}, {‘good’: 3, ‘Gfg’: ‘xcvz’}, {‘good’: 4, ‘Gfg’: None}]The maximum length key value : 8
 
Method #2 : Using list comprehension + len() + max() (one liner)The similar task can also be combined to perform in one line for compact solution.
# Python3 code to demonstrate working of # Maximum String value length of Key# Using max() + len() + list comprehension (one liner)  # initializing listtest_list = [{'Gfg' :  "abcd", 'best' : 2},              {'Gfg' :  "qwertyui", 'best' : 2},             {'Gfg' :  "xcvz", 'good' : 3},             {'Gfg' : None, 'good' : 4}]  # printing original listprint("The original list is : " + str(test_list))  # initializing Key filt_key = 'Gfg'  # Maximum String value length of Key# Using max() + len() + list comprehension (one liner)res = len(max(test_list, key = lambda sub: len(sub[filt_key])                if sub[filt_key] is not None else 0)[filt_key])  # printing result print("The maximum length key value : " + str(res)) 
The original list is : [{‘best’: 2, ‘Gfg’: ‘abcd’}, {‘best’: 2, ‘Gfg’: ‘qwertyui’}, {‘good’: 3, ‘Gfg’: ‘xcvz’}, {‘good’: 4, ‘Gfg’: None}]The maximum length key value : 8
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