path

问题 Is there any way to convert Postgres PATH type to an ARRAY in order to have index access to it's points? 回答1: There is no way to do that with PostgreSQL alone - you'd have to write your own C function. With the PostGIS extension, you can cast the path to geometry and perform the operation there: SELECT array_agg(CAST(geom AS point)) FROM st_dumppoints(CAST(some_path AS geometry)); 来源： https://stackoverflow.com/questions/60389921/postgres-convert-path-type-to-array

问题 Is there any way to convert Postgres PATH type to an ARRAY in order to have index access to it's points? 回答1: There is no way to do that with PostgreSQL alone - you'd have to write your own C function. With the PostGIS extension, you can cast the path to geometry and perform the operation there: SELECT array_agg(CAST(geom AS point)) FROM st_dumppoints(CAST(some_path AS geometry)); 来源： https://stackoverflow.com/questions/60389921/postgres-convert-path-type-to-array

问题 I have a weighted graph,G, extracted from a text file: i j distance 1 2 6000 1 3 4000 2 1 6000 2 6 5000 .... And I have specific a route (not a shortest path) that I want to plot on graph G, i.e. [1, 2, 6, 7] that starts from node 1, end at node 7 by visiting node 2 and node 6. Here the code I've tried. But since Im new in python and networkx package as well, I couldn't get the result that Im looking for. G = nx.read_edgelist('Graph.txt', data=(('weight',float),)) r=[1,2,6,7] edges=[] route

问题 I have a weighted graph,G, extracted from a text file: i j distance 1 2 6000 1 3 4000 2 1 6000 2 6 5000 .... And I have specific a route (not a shortest path) that I want to plot on graph G, i.e. [1, 2, 6, 7] that starts from node 1, end at node 7 by visiting node 2 and node 6. Here the code I've tried. But since Im new in python and networkx package as well, I couldn't get the result that Im looking for. G = nx.read_edgelist('Graph.txt', data=(('weight',float),)) r=[1,2,6,7] edges=[] route

问题 Say we have a script that works with no problem: import module1 class SomeClass(object): def __init__(self): self.m = module1() s = SomeCLass() However if I use multiprocessing module with "spawn" context: import module1 import multiprocessing as mp class SomeClass(object): def __init__(self): self.m = module1() s = SomeCLass() ctx = mp.get_context('spawn') proc = ctx.Process(target=SomeClass, kwargs={}) proc.daemon = True proc.start() I get the following error at proc.start() :

问题 Say we have a script that works with no problem: import module1 class SomeClass(object): def __init__(self): self.m = module1() s = SomeCLass() However if I use multiprocessing module with "spawn" context: import module1 import multiprocessing as mp class SomeClass(object): def __init__(self): self.m = module1() s = SomeCLass() ctx = mp.get_context('spawn') proc = ctx.Process(target=SomeClass, kwargs={}) proc.daemon = True proc.start() I get the following error at proc.start() :

问题 I am working on a little project in python for work. It involves opening a file with the os.startfile() And there in lies my problem : the path to the file contains several numbers. And for some reason I don't understand this cause problems in locating the file. Is there a work around for this? Because I can't change the names of the directory or the file. 回答1: The problem is that the \ character has a special meaning in python, e.g. \n is a newline etc. You can either do: os.startfile(r"G:

问题 I am trying to run the osmar package on my windows 10, R 3.4.2, and have correctly installed osmosis. However when I try to run the code: >library("osmar") > >src <- osmsource_osmosis(file = "c:/users/ben_c/Documents/FYP/FYP_NL_Map/muenchen.osm", osmosis = "osmosis") > > >nl_bbox <- center_bbox(11.575278, 48.137222, 3000, 3000) > >nl <- get_osm(nl_bbox, src) > >plot(nl) I get the warning, after osmosis has run: >Error in file(con, "r") : cannot open the connection >In addition: Warning

问题 I am trying to run the osmar package on my windows 10, R 3.4.2, and have correctly installed osmosis. However when I try to run the code: >library("osmar") > >src <- osmsource_osmosis(file = "c:/users/ben_c/Documents/FYP/FYP_NL_Map/muenchen.osm", osmosis = "osmosis") > > >nl_bbox <- center_bbox(11.575278, 48.137222, 3000, 3000) > >nl <- get_osm(nl_bbox, src) > >plot(nl) I get the warning, after osmosis has run: >Error in file(con, "r") : cannot open the connection >In addition: Warning

问题 I am trying to run the osmar package on my windows 10, R 3.4.2, and have correctly installed osmosis. However when I try to run the code: >library("osmar") > >src <- osmsource_osmosis(file = "c:/users/ben_c/Documents/FYP/FYP_NL_Map/muenchen.osm", osmosis = "osmosis") > > >nl_bbox <- center_bbox(11.575278, 48.137222, 3000, 3000) > >nl <- get_osm(nl_bbox, src) > >plot(nl) I get the warning, after osmosis has run: >Error in file(con, "r") : cannot open the connection >In addition: Warning