in-place

Would it be possible to mutate DataFrame inplace with groupby statement? import pandas as pd dt = pd.DataFrame({ "LETTER": ["a", "b", "c", "a", "b"], "VALUE" : [10 , 12 , 13, 0, 15] }) def __add_new_col(dt_): dt_['NEW_COL'] = dt_['VALUE'] - dt_['VALUE'].mean() return dt_ pass dt.groupby("LETTER").apply(__add_new_col) LETTER VALUE NEW_COL 0 a 10 5.0 1 b 12 -1.5 2 c 13 0.0 3 a 0 -5.0 4 b 15 1.5 dt LETTER VALUE 0 a 10 1 b 12 2 c 13 3 a 0 4 b 15 In R data.table it is possible by using := operator e.g. dt[, col := ... , by ='LETTER'] I think you can use transform which return Series same length and

In cygwin, the following code works fine $ cat junk bat bat bat $ cat junk | sort -k1,1 |tr 'b' 'z' > junk $ cat junk zat zat zat But in the linux shell(GNU/Linux), it seems that overwriting doesn't work [41] othershell: cat junk cat cat cat [42] othershell: cat junk |sort -k1,1 |tr 'c' 'z' zat zat zat [43] othershell: cat junk |sort -k1,1 |tr 'c' 'z' > junk [44] othershell: cat junk Both environments run BASH. I am asking this because sometimes after I do text manipulation, because of this caveat, I am forced to make the tmp file. But I know in Perl, you can give "i" flag to overwrite the

I have a program that has a number of filenames configured internally. The program edits a bunch of configuration files associated with a database account, and then changes the database password for the database account. The list of configuration files is associated with the name of the database account via an internal list. When I process these files, I have the following loop in my program: BEGIN { $^I = '.oldPW'; } # Enable in-place editing ... foreach (@{$Services{$request}{'files'}}) { my $filename = $Services{$request}{'configDir'} . '/' . $_; print "Processing ${filename}\n"; open

Given an array [a1b7c3d2] convert to [abcd1732] with O(1) space and O(n) time i.e. put the letters on the left and digits on the right such that their relative order is the same. I can think of an O(nlogn) algorithm, but not better. Can somebody please help? AFAIK it can't be done. This is essentially a single step of the RADIX sort algorithm. And AFAIK stable RADIX sort can't be done in-place. edit Wikipedia agrees with me (for what that's worth): http://en.wikipedia.org/wiki/Radix_sort#Stable_MSD_radix_sort_implementations MSD Radix Sort can be implemented as a stable algorithm, but requires

Are there any tools / UNIX single liners which would remove trailing whitespaces for multiple files in-place . E.g. one that could be used in the conjunction with find . You want sed --in-place 's/[[:space:]]\+$//' file That will delete all POSIX standard defined whitespace characters, including vertical tab and form feed. Also, it will only do a replacement if the trailing whitespace actually exists, unlike the other answers that use the zero or more matcher ( * ). --in-place is simply the long form of -i . I prefer to use the long form in scripts because it tends to be more illustrative of

I wrote a small quicksort implementation in matlab to sort some custom data. Because I am sorting a cell-array and I need the indexes of the sort-order and do not want to restructure the cell-array itself I need my own implementation (maybe there is one available that works, but I did not find it). My current implementation works by partitioning into a left and right array and then passing these arrays to the recursive call. Because I do not know the size of left and and right I just grow them inside a loop which I know is horribly slow in matlab. I know you can do an in place quicksort, but I

I'm making a small program for math (no particular reason, just kind of wanted to) and I ran into the error "TypeError: 'NoneType' object is not subscriptable. I have never before seen this error, so I have no idea what it means. import math print("The format you should consider:") print str("value 1a")+str(" + ")+str("value 2")+str(" = ")+str("value 3a ")+str("value 4")+str("\n") print("Do not include the letters in the input, it automatically adds them") v1 = input("Value 1: ") v2 = input("Value 2: ") v3 = input("Value 3: ") v4 = input("Value 4: ") lista = [v1, v3] lista = list.sort(lista) a