Sometimes, while working with data, we can have a problem in which we need to filter the strings list in such a way that strings ending with specific suffixes are removed. Let’s discuss certain ways in which this task can be performed.
Method #1 : Using loop + remove() + endswith() Method
The combination of the above functions can solve this problem. In this, we remove the elements that end with a particular suffix accessed using a loop and return the modified list.
Python3
# Python3 code to demonstrate working of# Suffix removal from String list# using loop + remove() + endswith()# initialize listtest_list = ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx']# printing original listprint("The original list : " + str(test_list))# initialize suffixsuff = 'x'# Suffix removal from String list# using loop + remove() + endswith()for word in test_list[:]: if word.endswith(suff): test_list.remove(word)# printing resultprint("List after removal of suffix elements : "+ str(test_list)) |
The original list : ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx'] List after removal of suffix elements : ['gfg', 'xit', 'is']
Time Complexity: O(n)
Auxiliary Space: O(1)
Method #2: Using list comprehension + endswith() Method
This is another way in which this task can be performed. In this, we don’t perform the removal in place, instead, we recreate the list without the elements that match the suffix.
Python3
# Python3 code to demonstrate working of# Suffix removal from String list# using list comprehension + endswith()# initialize listtest_list = ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx']# printing original listprint("The original list : " + str(test_list))# initialize suffsuff = 'x'# Suffix removal from String list# using list comprehension + endswith()res = [ele for ele in test_list if not ele.endswith(suff)]# printing resultprint("List after removal of suffix elements : "+ str(res)) |
The original list : ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx'] List after removal of suffix elements : ['gfg', 'xit', 'is']
Time Complexity: O(n)
Auxiliary Space: O(n)
Method#3: Using filter function + endswith() Method
This is another way in which a task can be performed. In this, we can create a new list with the help of a filter function which filters out all the string which ends with a defined suffix.
Python3
# Python3 code to demonstrate working of# Remove prefix strings from list# using filter + endswith()# initialize suffsuff = 'x'def eva(x): return not x.endswith(suff)# initialize listtest_list = ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx']# printing original listprint("The original list : " + str(test_list))# Remove prefix strings from list# using filter + endswith()res = list(filter(eva, test_list))# printing resultprint("List after removal of Kth character of each string : " + str(res)) |
The original list : ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx'] List after removal of Kth character of each string : ['gfg', 'xit', 'is']
Time Complexity: O(n)
Auxiliary Space: O(n)
Method #4 : Without any built-in methods
Python3
# Python3 code to demonstrate working of# Suffix removal from String list# initialize listtest_list = ["allx", "lovex", "gfg", "xit", "is", "bestx"]# printing original listprint("The original list : " + str(test_list))# initialize suffixsuff = "x"res = []# Suffix removal from String listfor i in test_list: if(i[-1] != suff): res.append(i)# printing resultprint("List after removal of suffix elements : " + str(res)) |
The original list : ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx'] List after removal of suffix elements : ['gfg', 'xit', 'is']
Time Complexity: O(n)
Auxiliary Space: O(n)
Method #5 : Using find() and len() methods
Python3
# Python3 code to demonstrate working of# Suffix removal from String list# initialize listtest_list = ["allx", "lovex", "gfg", "xit", "is", "bestx"]# printing original listprint("The original list : " + str(test_list))# initialize suffixsuff = "x"res = []# Suffix removal from String listfor i in test_list: if(i.find(suff)!=len(i)-1): res.append(i)# printing resultprint("List after removal of suffix elements : " + str(res)) |
The original list : ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx'] List after removal of suffix elements : ['gfg', 'xit', 'is']
Time Complexity: O(n)
Auxiliary Space: O(n)
Method #6 : Using lambda functions
Python3
# Python3 code to demonstrate working of# Remove prefix strings from list# initialize suffsuff = 'x'# initialize listtest_list = ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx']# printing original listprint("The original list : " + str(test_list))# Remove prefix strings from listres = list(filter(lambda x: x[-1] != suff, test_list))# printing resultprint("List after removal of Kth character of each string : " + str(res)) |
The original list : ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx'] List after removal of Kth character of each string : ['gfg', 'xit', 'is']
Time Complexity: O(n)
Auxiliary Space: O(n)
Method #7 : Using Regular Expressions
This method uses the regular expression module ‘re’ to match the strings in the list that end with a specific suffix and remove them. Here is an example of how it can be done:
Python3
import re# initialize listtest_list = ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx']# printing original listprint("The original list : " + str(test_list))# initialize suffixsuff = 'x$'# Suffix removal from String list using regular expressionsres = [x for x in test_list if not re.search(suff, x)]# printing resultprint("List after removal of suffix elements : " + str(res))#This code is contributed by Edula Vinay Kumar Reddy |
The original list : ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx'] List after removal of suffix elements : ['gfg', 'xit', 'is']
Time Complexity: O(n)
Auxiliary Space: O(n)
Here we use the function re.search() which returns a match object if there is a match anywhere in the string. We use this function in a list comprehension to filter out the elements in the list that match the regular expression.
Method#8: Using pandas
Python3
import pandas as pdtest_list = ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx']# printing original listprint("The original list : " + str(test_list))suffix = 'x'# Convert the list of strings to a pandas seriess = pd.Series(test_list)# Remove elements with the suffixres = s[~s.str.endswith(suffix)].tolist()print("List after removal of suffix elements :", res)#This code is contributed by Vinay Pinjala. |
Output
The original list : ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx'] List after removal of suffix elements : ['gfg', 'xit', 'is']
Time Complexity: O(n)
Auxiliary Space: O(n)
Method#8: Recursive method
Algorithm:
- Define a function remove_strings_with_prefix(lst, prefix) that takes in a list lst and a prefix prefix, and returns a new list that includes only those strings in lst that do not end with the prefix.
- Check for the base case where the input list is empty. If the list is empty, return an empty list.
- For the recursive case, remove the prefix from the first element in the list, head, and check whether the resulting string still ends with the prefix.
- If the head element still ends with the prefix, skip it and recurse on the rest of the list by calling remove_strings_with_prefix(lst[1:], prefix).
- If the head element does not end with the prefix, include it in the result by returning [head] + remove_strings_with_prefix(lst[1:], prefix).
- Return the resulting list after all recursive calls have completed.
Python3
def remove_strings_with_prefix(lst, prefix): # Base case: if the list is empty, return an empty list if not lst: return [] # Recursive case: remove the prefix from the first element in the list head = lst[0] if head.endswith(prefix): # If the head ends with the prefix, skip it and recurse on the rest of the list return remove_strings_with_prefix(lst[1:], prefix) else: # If the head does not end with the prefix, include it and recurse on the rest of the list return [head] + remove_strings_with_prefix(lst[1:], prefix)test_list = ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx']# printing original listprint("The original list : " + str(test_list))suffix = 'x'# Remove elements with the suffixres = remove_strings_with_prefix(test_list,suffix)print("List after removal of suffix elements :", res)#This code is contributed by tvsk. |
The original list : ['allx', 'lovex', 'gfg', 'xit', 'is', 'bestx'] List after removal of suffix elements : ['gfg', 'xit', 'is']
The time complexity of this method is O(n), where n is the length of the input list, because it processes each element of the list exactly once. The worst-case time complexity occurs when none of the strings in the input list end with the prefix, in which case the method makes n recursive calls. The best-case time complexity occurs when all the strings in the input list end with the prefix, in which case the method makes only one recursive call.
The space complexity of this method is also O(n), because it creates a new list with at most n elements in the worst case. This is because the method creates a new list for each recursive call and concatenates the resulting lists together at each level of recursion. However, in the best case where all the strings in the input list end with the prefix, the method returns the original input list and therefore does not create any new lists.
