concatenation

来源： https://stackoverflow.com/questions/63459142/how-to-get-many-rolling-window-slices-in-numpy

来源： https://stackoverflow.com/questions/63332234/text-and-jsonb-concatenation-in-a-single-postgresql-query

来源： https://stackoverflow.com/questions/62706573/how-to-concatenate-to-string-correctly

问题 This question already has answers here : Putting char into a java string for each N characters (11 answers) Closed 4 years ago . In Android if I have an edit text and the user entered 123456789012, how could I get the program to insert a dash every 4th character. ie: 1234-5678-9012 ? I guess you need to say something along the lines of:- a=Characters 1~4, b=Characters 5~8, c=Characters 9-12 , Result = a + "-" + b + "-" + c . But I am unsure of how that would look in Android. Many thanks for

问题 I would like to concatenate my files. I use cat *txt > newFile But I have almost 500000 files and it complains that the argument list is too long. Is there an efficient and fast way of merging half a million files? Thanks 回答1: If your directory structure is shallow (there are no subdirectories) then you can simply do: find . -type f -exec cat {} \; > newFile If you have subdirectories, you can limit the find to the top level, or you might consider putting some of the files in the sub

问题 Suppose I have the following dataframe: pd.DataFrame({'col1': ["a", "a", np.nan, np.nan, np.nan], 'override1': ["b", np.nan, "b", np.nan, np.nan], 'override2': ["c", np.nan, np.nan, "c", np.nan]}) col1 override1 override2 0 a b c 1 a NaN NaN 2 NaN b NaN 3 NaN NaN c 4 NaN NaN NaN Is there a way to collapse the 3 columns into one column, where override2 overrides override1 , which overrides col1 , however, in case there is NaN, then the values bofore is to be kept? Also, I am mainly looking for

问题 Suppose I have the following dataframe: pd.DataFrame({'col1': ["a", "a", np.nan, np.nan, np.nan], 'override1': ["b", np.nan, "b", np.nan, np.nan], 'override2': ["c", np.nan, np.nan, "c", np.nan]}) col1 override1 override2 0 a b c 1 a NaN NaN 2 NaN b NaN 3 NaN NaN c 4 NaN NaN NaN Is there a way to collapse the 3 columns into one column, where override2 overrides override1 , which overrides col1 , however, in case there is NaN, then the values bofore is to be kept? Also, I am mainly looking for

问题 I need to flatten all the levels of a multi-level list: import itertools pool = [[[[[0,2],[1,3]],[[3,2],[1,0]]],"PdPd","PrisonerDilemma"], [[[[0,3],[1,2]],[[2,3],[1,0]]],"ShSh","StagHunt"], [[[[1,2],[3,0]],[[3,2],[1,0]]],"ChCh","Chicken"], [[[[2,1],[0,3]],[[3,1],[0,2]]],"BaBa","Battle"]] def flat3 (pool): for game in pool: l = list(itertools.chain.from_iterable(game[0])) print(l) The result: flat3 (pool) [[0, 2], [1, 3], [3, 2], [1, 0]] [[0, 3], [1, 2], [2, 3], [1, 0]] [[1, 2], [3, 0], [3, 2]

问题 I need to flatten all the levels of a multi-level list: import itertools pool = [[[[[0,2],[1,3]],[[3,2],[1,0]]],"PdPd","PrisonerDilemma"], [[[[0,3],[1,2]],[[2,3],[1,0]]],"ShSh","StagHunt"], [[[[1,2],[3,0]],[[3,2],[1,0]]],"ChCh","Chicken"], [[[[2,1],[0,3]],[[3,1],[0,2]]],"BaBa","Battle"]] def flat3 (pool): for game in pool: l = list(itertools.chain.from_iterable(game[0])) print(l) The result: flat3 (pool) [[0, 2], [1, 3], [3, 2], [1, 0]] [[0, 3], [1, 2], [2, 3], [1, 0]] [[1, 2], [3, 0], [3, 2]

问题 I need to flatten all the levels of a multi-level list: import itertools pool = [[[[[0,2],[1,3]],[[3,2],[1,0]]],"PdPd","PrisonerDilemma"], [[[[0,3],[1,2]],[[2,3],[1,0]]],"ShSh","StagHunt"], [[[[1,2],[3,0]],[[3,2],[1,0]]],"ChCh","Chicken"], [[[[2,1],[0,3]],[[3,1],[0,2]]],"BaBa","Battle"]] def flat3 (pool): for game in pool: l = list(itertools.chain.from_iterable(game[0])) print(l) The result: flat3 (pool) [[0, 2], [1, 3], [3, 2], [1, 0]] [[0, 3], [1, 2], [2, 3], [1, 0]] [[1, 2], [3, 0], [3, 2]