Meaning of list[-1] in Python - Stack Overflow I have a piece of code here that is supposed to return the least common element in a list of elements, ordered by commonality: def getSingle(arr): from collections import Counter c = Counte
What is the difference between list[1] and list[1:] in Python? By using a : colon in the list index, you are asking for a slice, which is always another list In Python you can assign values to both an individual item in a list, and to a slice of the list
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: list of lists - Stack Overflow The first, [:], is creating a slice (normally often used for getting just part of a list), which happens to contain the entire list, and thus is effectively a copy of the list The second, list(), is using the actual list type constructor to create a new list which has contents equal to the first list
python - if else in a list comprehension - Stack Overflow Since a list comprehension creates a list, it shouldn't be used if creating a list is not the goal; it shouldn't be used simply to write a one-line for-loop; so refrain from writing [print(x) for x in range(5)] for example
How can I pass a list as a command-line argument with argparse? Don't use quotes on the command line 1 Don't use type=list, as it will return a list of lists This happens because under the hood argparse uses the value of type to coerce each individual given argument you your chosen type, not the aggregate of all arguments You can use type=int (or whatever) to get a list of ints (or whatever)
How to group dataframe rows into list in pandas groupby Given a dataframe, I want to groupby the first column and get second column as lists in rows, so that a dataframe like: a b A 1 A 2 B 5 B 5 B 4 C 6 becomes A [1,2] B [5,5,4] C [6] How do I do this?
日历月历