feat: remove_elements_list - Remove elements not matching certain pattern - the fast way

Author: DahlitzFlorian

ebook/chapters/standard_lib_chapters/lists.tex

@@ -65,3 +65,16 @@ \subsection{Unpacking Lists Using * Operator}
 b = [2, 3, 4]
 c = 5
 \end{lstlisting}
+
+
+\subsection{Remove Elements Not Matching Pattern}
+
+Let's assume you have a list of certain data and want to remove all elements in it, which are not matching a certain pattern.
+You could make use of the built-in \lstinline{list.remove()} method, which removes the first match of and then shifts all subsequent data one position to the left.
+So, if you want to remove all, you need to loop over it.
+However, this approach gives quadratic behaviour.
+The following Listing shows you a much better way to achieve this:
+
+\lstinputlisting[caption=remove\_elements\_list.py]{../standard_lib/remove_elements_list.py}
+
+This approach is not only faster, but creates a new, distinct list and then replaces the old contents all at once.

ebook/python-snippets.epub

@@ -48,6 +48,7 @@ A collection of useful snippets using only the standard library.
 | reduce_memory_consumption_iterator | Shows how to reduce memory consumption by using itertools.repeat |
 | regular_expression_debug | Display debug information about the compiled regular expression with re.DEBUG flag |
 | remove_duplicates_list | Remove duplicates from list and keep the order |
+| remove_elements_list | Remove elements not matching certain pattern - the fast way! |
 | save_dict_update_without_loosing_original | Update dict value without loosing original value |
 | scopes_namespaces | Reveils the differences between `global`, `local`, and `nonlocal` |
 | set_union_intersection | Use \| and & for set union and intersection |

ebook/python-snippets.mobi

@@ -0,0 +1,8 @@
+data = [1, 2, 3, 4, 1, 2, 3, 4]
+target = 1
+
+print(f"Original: {data}")
+
+data[:] = [elem for elem in data if elem != target]
+
+print(f"New: {data}")