lst = [["aaaa8"],["bb8"],["ccc8"],["dddddd8"]...]
msg = filter[lambda x : x != "8", lst]
print msg
EDIT: For anyone who came across this post, just for understanding the above removes any elements from the list which are equal to 8.
Supposing we use the above example the first element ["aaaaa8"] would not be equal to 8 and so it would be dropped.
To make this [kinda work?] with how the intent of the question was we could perform something similar to this
msg = filter[lambda x: x != "8", map[lambda y: list[y], lst]]
- I am not in an interpreter at the moment so of course mileage may vary, we may have to index so we do list[y[0]] would be the only modification to the above for this explanation purposes.
What this does is split each element of list up into an array of characters so ["aaaa8"] would become ["a", "a", "a", "a", "8"].
This would result in a data type that looks like this
msg = [["a", "a", "a", "a"], ["b", "b"]...]
So finally to wrap that up we would have to map it to bring them all back into the same type roughly
msg = list[map[lambda q: ''.join[q], filter[lambda x: x != "8", map[lambda y: list[y[0]], lst]]]]
I would absolutely not recommend it, but if you were really wanting to play with map and filter, that would be how I think you could do it with a single line.
In this article, we will discuss different ways to remove a character from a list of strings in python. Suppose we have a list of strings, Now, we want to remove all occurrences of character ‘w’ rom this list of strings. After that list should be like this, There are different ways to do this. Let’s discuss them one by
one, Strings are immutable in python, so we can not modify them in place. But we can create a new string with the modified contents. So create a new list with the modified strings and then assign it back to the original variable. Advertisements For that, use the list comprehension to iterate over all strings in the list. Then for each string, call the replace[] function to
replace all occurrences of the character to be deleted with an empty string. Finally list comprehension will return a new list of modified strings. Let’s see it in working code, Output: It deleted all occurrences of character ‘w’ from the list of strings. We can also use the map[] function to remove a character from all the strings in a list. Steps are as follows, Working example is as follows, Output: It deleted all occurrences of character ‘w’ from the list of strings. Summary: We learned about two different ways to delete a character from a list of strings in python.list_of_str = ['what', 'why', 'now', 'where', 'who', 'how', 'wow']
['hat', 'hy', 'no', 'here', 'ho', 'ho', 'o']
Remove a character from list of strings using list comprehension and replace[]
list_of_str = ['what', 'why', 'now', 'where', 'who', 'how', 'wow']
ch = 'w'
# Remove character 'w' from the list of strings
list_of_str = [elem.replace[ch, ''] for elem in list_of_str]
print[list_of_str]
['hat', 'hy', 'no', 'here', 'ho', 'ho', 'o']
Remove a character from list of strings using map[] function
list_of_str = ['what', 'why', 'now', 'where', 'who', 'how', 'wow']
# Remove character 'w' from the list of strings
list_of_str = list[map[lambda elem: elem.replace[ch, ''], list_of_str]]
print[list_of_str]
['hat', 'hy', 'no', 'here', 'ho', 'ho', 'o']
Master in Python Programming Certification is one of the most sought after certifications in the market. The reason for this is the array of functionalities Python offers. Lists are one collection that simplifies the life of programmers to a great extent. In this article, we shall learn one such feature that is how to remove elements from lists.
Before moving on, let’s take a quick look at all that is covered in this article:
Why use Lists?
What are Lists?
Remove Elements from List using:
- remove[]
- pop[]
- del[]
So let’s get started. :]
Why use Lists?
Sometimes, there may be situations where you need to handle different types of data at the same time. For example, let’s say, you need to have a string type element, an integer and a floating-point number in the same collection. Now, this is fairly impossible with the default data types that are available in other programming languages like C & C++. In simple words, if you define an array of type integer, you can only store integers in it. This is where Python has an advantage. With its list collection data type, we can store elements of different data types as a single ordered collection!
Now that you know how important lists are, let’s move on to see what exactly are Lists and how to remove elements from list!
What are Lists?
Lists are ordered sequences that can hold a variety of object types. In other words, a list is a collection of elements which is ordered and changeable. Lists also allow duplicate members. We can compare lists in Python to arrays in other programming languages. But, there’s one major difference. Arrays contain elements of the same data types, whereas Python lists can contain items of different types. A single list may contain data types like strings, integers, floating point numbers etc. Lists support indexing and slicing, just like strings. Lists are also mutable, which means, they can be altered after creation. In addition to this, lists can be nested as well i.e. you could include a list within a list.
The main reason why lists are an important tool in Python Programming is because of the wide variety of the built-in functions it comes with. Lists are also very useful to implement stacks and queues in Python. All the elements in a list are enclosed within ‘square brackets’, and every element in it are separated by a ‘comma’.
EXAMPLE:
myList = ["Bran",11,3.14,33,"Stark",22,33,11] print[myList]
OUTPUT: [‘Bran’, 11, 3.14, 33, ‘Stark’, 22, 33, 11]
In the
above example, we have defined a list called ‘myList’. As you can see, all the elements are enclosed within square brackets i.e. [ ] and each element is separated by a comma. This list is an ordered sequence that contains elements of different data types.
At index 0, we have the string element ‘Bran’.
At index 1, we have an integer 11.
At index 2, we have a floating-point number 3.14.
In this way, we can store elements of different types in a single list.
Now that you have a clear idea about how you can actually create lists, let’s move on to see, how to Remove Elements from Lists in Python.
There are three ways in which you can Remove elements from List:
- Using the remove[] method
- Using the list object’s pop[] method
- Using the del operator
Let’s look at these in detail.
List Object’s remove[] method:
The remove[] method is one of the most commonly used list object methods to remove an item or an element from the list. When you use this method, you will need to specify the particular item that is to be removed. Note that, if there are multiple occurrences of the item specified, then its first occurrence will be removed from the list. We can consider this method as “removal by item’s value”. If the particular item to be removed is not found, then a ValueError is raised.
Consider the following examples:
EXAMPLE 1:
myList = ["Bran",11,22,33,"Stark",22,33,11] myList.remove[22] myList
OUTPUT: [‘Bran’, 11, 33, ‘Stark’, 22, 33, 11]
In this example, we are defining a list called ‘myList’. Note that, as discussed before, we are enclosing the list literal within square brackets. In Example 1, we are using the remove[] method to remove the element 22 from myList. Hence, when printing the list using the print[], we can see that the element 22 has been removed from myList.
EXAMPLE 2:
myList.remove[44]
OUTPUT:
Traceback [most recent call last]:
File “”, line 1, in
ValueError: list.remove[x]: x not in list2
In Example 2, we use the remove[] to remove the element 44. But, we know that the list ‘myList’ does not have the integer 44. As a result, a ‘ValueError’ is thrown by the Python interpreter.
[However, this is a slow technique, as it involves searching the item in the list.]
List Object’s pop[] method:
The pop[] method is another commonly used list object method. This method removes an item or an element from the list, and returns it. The difference between this method and the remove[] method is that, we should specify the item to be removed in the remove[] method. But, when using the pop[], we specify the index of the item as the argument, and hence, it pops out the item to be returned at the specified index. If the particular item to be removed is not found, then an IndexError is raised.
Consider the following examples:
EXAMPLE 1:
myList = ["Bran",11,22,33,"Stark",22,33,11] myList.pop[1]
Output: 11
In this example, we are defining a list called ‘myList’. In Example 1, we are using the pop[ ] method, while passing the argument ‘1’, which is nothing but the index position 1. As you can see from the output, the pop[ ] removes the element, and returns it, which is the integer ‘11’.
EXAMPLE 2:
myList
OUTPUT: [‘Bran’, 22, 33, ‘Stark’, 22, 33, 11]
Note that, in Example 2, when we print the list myList after calling pop[], the integer 11, which was previously present in myList has been removed.
EXAMPLE 3:
myList.pop[8]
OUTPUT:
Traceback [most recent call last]:
File “”, line 1, in
IndexError: pop index out of range
In Example 3, we use the pop[] to remove the element which is at index position 8. Since there is no element at this position, the python interpreter throws an IndexError as shown in output.
[This is a fast technique, as it is pretty straightforward, and does not involve any searching of an item in the list.]
Python del operator:
This operator is similar to the List object’s pop[] method with one important difference. The del operator removes the item or an element at the specified index location from the list, but the removed item is not returned, as it is with the pop[] method. So essentially, this operator takes the item’s index to be removed as the argument and deletes the item at that index. The operator also supports removing a range of items in the list. Please note, this operator, just like the pop[] method, raises an IndexError, when the index or the indices specified are out of range.
Consider the following examples:
EXAMPLE 1:
myList = ["Bran",11,22,33,"Stark",22,33,11] del myList[2] myList
OUTPUT: [‘Bran’, 11, 33, ‘Stark’, 22, 33, 11]
In the above example, we are defining a list called ‘myList’. In Example 1, we use the del operator to delete the element at index position 2 in myList. Hence, when you print myList, the integer ‘22’ at index position 2 is removed, as seen in the output.
EXAMPLE 2:
del myList[1:4] myList
OUTPUT: [‘Bran’, 22, 33, 11]
In Example 2, we use the del operator to remove elements from a range of indices, i.e. from index position 1 till index position 4 [but not including 4]. Subsequently, when you print myList, you can see the elements at index position 1,2 and 3 are removed.
EXAMPLE 3:
del myList[7]
OUTPUT:
Traceback [most recent call last]:
File “”, line 1, in
IndexError: list assignment index out of range
In Example 3, when you use the del operator to remove an element at index position 7 [which does not exist], the python interpreter throws a ValueError.
[This technique of removing items is preferred when the user has a clear knowledge of the items in the list. Also, this is a fast method to remove items from a list.]
To summarize, the remove[] method removes the first matching value, and not a specified index; the pop[] method removes the item at a specified index, and returns it; and finally the del operator just deletes the item at a specified index [ or a range of indices].
Footnotes- Most popular questions asked related to Removing Element from a List
How do I remove a specific element from a list in Python?
The remove[] method removes the first matching element [which is passed as an argument] from the list. The pop[] method removes an element at a given index, and will also return the removed item. You can also use the del keyword in Python to remove an element or slice from a list.
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How do I remove the first element from a list in Python?
We can do it vie these four options:
- list.pop[] –
The simplest approach is to use list’s pop[[i]] method which removes and returns an item present at the specified position in the list. - list.remove[] –
This is another approach where the method remove[x] removes the first item from the list which matches the specified value. - Slicing –
To remove the first item we can use Slicing by obtaining a sublist containing all items of the list except the first one. - The del statement –
Using Del statement, we can remove an item from a list using its index.The difference compared to pop[] method is, that this does not return the removed element.
How do you remove the last element of a list in Python?
The method pop[] can be used to remove and return the last value from the list or the given index value. If the index is not given, then the last element is popped out and removed.
How do I remove multiple elements from a list in Python?
Even for this purpose, Del keywords can be used. It will remove multiple elements from a list if we provide an index range. To remove multiple elements from a list in index positions 2 to 5, we should use the del method which will remove elements in range from index2 to index5.
I hope you were able to go through this article and get a fair understanding of the various techniques to Remove Elements from List.
Make sure you practice as much as possible and revert your experience.
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