Demonstrates that evaluating wcs.pixel_to_world is efficient for large vectors but very inefficient for single calls.

pix2world_timing.py

from time import sleep, time
import numpy as np
from astropy import wcs

w = wcs.WCS(naxis=2)
w.wcs.ctype = ["RA---SIN","DEC--SIN"]
w.wcs.cdelt = (6.2/3600, 6.2/3600)
w.wcs.crval = (30, 60)
w.wcs.crota = (0, 15)
# ----------------------------------------    
N = 100
xs=np.random.randint(0, 128, N)
ys=np.random.randint(0, 128, N)
t1 = time()
M = 100
for i in range(M):
    coord = w.pixel_to_world(xs, ys)
t2 = time()

print('I.  Process duration for array of size N = {}: {:.3f} ms per iteration'.format(N, (t2-t1)/M*1000))

# ----------------------------------------    
N = 1000
xs=np.random.randint(0, 128, N)
ys=np.random.randint(0, 128, N)
t1 = time()

for i in range(M):
    coord = w.pixel_to_world(xs, ys)
t2 = time()

print('II. Process duration for array of size N = {}: {:.3f} ms per iteration'.format(N, (t2-t1)/M*1000))