Python - Remove String from String List
Last Updated : 24 Mar, 2023
This particular article is indeed a very useful one for Machine Learning enthusiast as it solves a good problem for them. In Machine Learning we generally encounter this issue of getting a particular string in huge amount of data and handling that sometimes becomes a tedious task. Lets discuss certain way outs to solve this problem.
Method #1: Using remove() This particular method is quite naive and not recommended to use, but is indeed a method to perform this task. remove() generally removes the first occurrence of K string and we keep iterating this process until no K string is found in list.
Python3 # Python 3 code to demonstrate # Remove K String from String List # using remove() # initializing list test_list = ["bad", "GeeksforGeeks", "bad", "is", "best", "bad"] # Printing original list print("Original list is : " + str(test_list)) # initializing K K = "bad" # using remove() to # Remove K String from String List while(K in test_list): test_list.remove(K) # Printing modified list print("Modified list is : " + str(test_list)) Output : Original list is : ['bad', 'GeeksforGeeks', 'bad', 'is', 'best', 'bad'] Modified list is : ['GeeksforGeeks', 'is', 'best']
Time Complexity: O(n), where n is the number of elements in the list “test_list”.
Auxiliary Space: O(1), constant extra space is required
Method #2: Using List Comprehension More concise and better approach to remove all the K strings, it just checks if the string is not K and re-makes the list with all strings that are not K.
Python3 # Python 3 code to demonstrate # Remove K String from String List # using list comprehension # initializing list test_list = ["bad", "GeeksforGeeks", "bad", "is", "best", "bad"] # Printing original list print("Original list is : " + str(test_list)) # initializing K K = "bad" # using list comprehension to # Remove K String from String List test_list = [i for i in test_list if i != K] # Printing modified list print("Modified list is : " + str(test_list)) Output : Original list is : ['bad', 'GeeksforGeeks', 'bad', 'is', 'best', 'bad'] Modified list is : ['GeeksforGeeks', 'is', 'best']
Time Complexity: O(n)
Auxiliary Space: O(n), where n is length of list.
Method #3 : Using join(),replace(),split() and remove() methods
Python3 # Python 3 code to demonstrate # Remove K String from String List # initializing list test_list = ["bad", "GeeksforGeeks", "bad", "is", "best", "bad"] # Printing original list print ("Original list is : " + str(test_list)) # initializing K K = "bad" x="-".join(test_list) x=x.replace(K,"") a=x.split("-") while("" in a ): a.remove("") # Printing modified list print ("Modified list is : " + str(a)) OutputOriginal list is : ['bad', 'GeeksforGeeks', 'bad', 'is', 'best', 'bad'] Modified list is : ['GeeksforGeeks', 'is', 'best']
Here's another approach to removing a string 'K' from a string list, using a filter:
Python # Python 3 code to demonstrate # Remove K String from String List # using filter() # initializing list test_list = ["bad", "GeeksforGeeks", "bad", "is", "best", "bad"] # Printing original list print("Original list is : " + str(test_list)) # initializing K K = "bad" # using filter to Remove K String from String List test_list = list(filter(lambda x: x!=K, test_list)) # Printing modified list print("Modified list is : " + str(test_list)) OutputOriginal list is : ['bad', 'GeeksforGeeks', 'bad', 'is', 'best', 'bad'] Modified list is : ['GeeksforGeeks', 'is', 'best']
This approach uses the filter() function to create a filtered list of elements from test_list that are not equal to K. The list() function is then used to convert the filtered list into a list.
Time complexity: O(n), where n is the number of elements in the list test_list.
Space complexity: O(n), since a new list is created.
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