slice - How slicing in Python works - Stack Overflow The first way works for a list or a string; the second way only works for a list, because slice assignment isn't allowed for strings Other than that I think the only difference is speed: it looks like it's a little faster the first way Try it yourself with timeit timeit() or preferably timeit repeat()
python - How to convert list to string - Stack Overflow Agree with @Bogdan This answer creates a string in which the list elements are joined together with no whitespace or comma in between You can use ', ' join(list1) to join the elements of the list with comma and whitespace or ' ' join(to) to join with only white space –
Use a list of values to select rows from a Pandas dataframe To select rows not in list_of_values, negate isin() in: df[~df['A'] isin(list_of_values)] df query("A not in @list_of_values") # df query("A != @list_of_values") 5 Select rows where multiple columns are in list_of_values If you want to filter using both (or multiple) columns, there's any() and all() to reduce columns (axis=1) depending on the
What is the difference between Pythons list methods append and extend . . . my_list + another_list creates a third list in memory, so you can return the result of it, but it requires that the second iterable be a list my_list += another_list modifies the list in-place (it is the in-place operator, and lists are mutable objects, as we've seen) so it does not create a new list It also works like extend, in that the
Best way to remove elements from a list - Stack Overflow This makes indexing a list a[i] an operation whose cost is independent of the size of the list or the value of the index When items are appended or inserted, the array of references is resized Some algorithm is applied to improve the performance of appending items repeatedly; when the array must be grown, some extra space is allocated so the
How to concatenate (join) items in a list to a single string @Wouter, it will not On the one hand, only lists of strings can be joined; so list join would be inappropriate for an arbitrary list On the other, the argument of str join can be any "iterable" sequence of strings, not just a list
Get a list from Pandas DataFrame column headers Create a list of keys columns - object method to_list() and the Pythonic way: my_dataframe keys() to_list() list(my_dataframe keys()) Basic iteration on a DataFrame returns column labels: [column for column in my_dataframe] Do not convert a DataFrame into a list, just to get the column labels
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