How do I make a variable for a nested loop?

Question

I have a bit of code that draws an array of lines (32X32 grid). The actual code that draws it starts from #Nested loop to draw anti-aliased lines in a 32X32 grid. Because I have a patch within it that has lines of different orientation, the codes is a few lines long.

At the moment, I have a .draw() at the end of the nested loop that draws my array.

It doesn't seem like a good way to do this.

Is there a way to create a variable for this entire nested loop so i can call it as and when I want? For instance myStim.draw()

# Import what is needed
import numpy as np
from psychopy import visual, event, core, logging
from math import sin, cos
import random, math

# Create space variables and a window
lineSpaceX = 0.55
lineSpaceY = 0.55

patch_orientation = 45 # zero is vertical, going anti-clockwise
surround_orientation = 90

#Jitter values
g_posJitter = 0.05 #gaussian positional jitter
r_posJitter = 0.05 #random positional jitter

g_oriJitter = 5 #gaussian orientation jitter
r_oriJitter = 5 #random orientation jitter

#Region where the rectangular patch would appear
x_rand=random.randint(6,13) #random.randint(Return random integers from low (inclusive) to high (inclusive).
y_rand=random.randint(6,16)

#rectangular patch dimensions
width=15
height=12

message = visual.TextStim(win,pos=(0.0,-12.0),text='...Press SPACE to continue...')

# Initialize clock to record response time
rt_clock = core.Clock()


#Nested loop to draw anti-aliased lines in a 32X32 grid
for x in xrange(1,33): #32x32 grid.
    for y in xrange(1,33): 
        ##Define x & y value (Gaussian distribution-positional jitter)
        x_pos = (x-32/2-1/2 )*lineSpaceX + random.gauss(0,g_posJitter) #random.gauss(mean,s.d); -1/2 is to center even-numbered stimuli; 32x32 grid
        y_pos = (y-32/2-1/2 )*lineSpaceY + random.gauss(0,g_posJitter)

        if (x >= x_rand and x < x_rand+width) and (y >= y_rand and y < y_rand+height): # note only "=" on one side
            Line_Orientation = random.gauss(patch_orientation,g_oriJitter) #random.gauss(mean,s.d) - Gaussian func.
        else:
            Line_Orientation = random.gauss(surround_orientation,g_oriJitter) #random.gauss(mean,s.d) - Gaussian func.
            #stimOri = random.uniform(xOri - r_oriJitter, xOri + r_oriJitter) #random.uniform(A,B) - Uniform func.
        visual.Line(win, units = "deg", start=(0,0), end=(0.0,0.35), pos=(x_pos,y_pos), ori=Line_Orientation, autoLog=False).draw() #Gaussian func.

frameN = 0
for frameN in range(80): #for exactly 80 frames; 1 frame = 16.67ms on the 1920 x 1080 monitor
    if frameN == 0:
        rt_clock.reset() # set reaction time clock to 0
    message.draw()
    win.flip()#   display stimulus 

    frameN = frameN + 1
    keys = event.waitKeys(keyList=['space', 'escape','q'])    #create key list response

    # handle key responses 
    if len(keys)>0:
        rt = rt_clock.getTime()
        if keys == ['space']:
            event.clearEvents()
            break
        else:
            print 'Stopped Early'
            win.close()
            core.quit()

print x_rand, y_rand 
print keys, rt  #display response and reaction time on screen output window

Answer 1

1. It's not a variable you want, but a function.

2. The way you are currently doing things (via visual.Line(...).draw()) is very inefficient. You're creating a new line on very iteration, just to draw it once, and not storing a reference to it. A much more time-efficient scheme is to create just a single line object instance, referenced with a variable name, and then on every iteration, simply update its attributes (orientation etc), before drawing it.

3. An alternative would be to create multiple line object instances once, but store each in a list. Then drawing them again as required is a simple matter of:

for line_instance in line_list:

    line_instance.draw()