python - Sorting by instructions -

i have vector/column length 1000 , values 1,2.

how can sort vector/column obtain result like:

1 2 1 2 1 2 etc.  

in r:

some sample-data:

x <- sample(1:2, 1000, replace = true) 

do:

x[match(rep(1:2, 500), x)]