I have a df like so: I want to flatten the df so it is one continuous list like so: [‘1/2/2014’, ‘a’, ‘6’, ‘z1’, ‘1/2/2014’, ‘a’, ‘3’, ‘z1′,’1/3/2014’, ‘c’, ‘1’, ‘x3’…
Tag: list
find and update a value of a dictionary in list of dictionaries
How can I find the dictionary with value user7 then update it’s match_sum eg add 3 to the existing 4. I have this, and am not sure if its the best practice to do it. Answer You can also use next(): prints: Note that if default (second argument) is not specified while calling next(), it would raise StopI…
Python: Length of longest common subsequence of lists
Is there a built-in function in python which returns a length of longest common subsequence of two lists? I tried to find longest common subsequence and then get length of it but I think there must be a better solution. Answer You can easily retool a Longest Common Subsequence (LCS) into a Length of the Longe…
Pop multiple items from the beginning and end of a list
Suppose I have a list of items like this: I want to pop two items from the left (i.e. a and b) and two items from the right (i.e. h,i). I want the most concise an clean way to do this. I could do it this way myself: Any other alternatives? Answer From a performance point of view: mylist =
How to get sorted list inside a dictionary with json.dumps()
I have the following problem: having a python dictionary like the following: I would like to obtain an ordered json object such as: At the moment I use the following: But the two list inside my object are not sorted, and I get: probably because the custom JSONEncoder skips a type that already knows how to man…
Replace special characters in a string in Python
I am using urllib to get a string of html from a website and need to put each word in the html document into a list. Here is the code I have so far. I keep getting an error. I have also copied the error below. Here is the error. Answer str.replace is the wrong function for what you want
Python quicksort – one list – swaps
**I need to make a quicksort algorithm but so that it uses only one list and does swaps inside of it. I managed to make it “sort” or position the first element but now i don’t know how to implement the recursion. The biggest problem I’m having is how to recursively work on a part of th…
Randomly extract x items from a list using python
Starting with two lists such as: I want to have the user input how many items they want to extract, as a percentage of the overall list length, and the same indices from each list to be randomly extracted. For example say I wanted 50% the output would be I have achieved this using the following code: But I wa…
What is the difference between `sorted(list)` vs `list.sort()`?
list.sort() sorts the list and replaces the original list, whereas sorted(list) returns a sorted copy of the list, without changing the original list. When is one preferred over the other? Which is more efficient? By how much? Can a list be reverted to the unsorted state after list.sort() has been performed? …
Wrapping around on a list when list index is out of range
I’m looking for some code improvement, or a pre-built version of what I’ve implemented myself as I think there might be, or should be, a cleaner way to achieve what I want. I’m writing a piece of software to convert guitar tabs into classical notation, I need to convert the number on a tab t…