Melanie Ann Tarr Melanie Ann Tarr - 3 years ago 481
Python Question

python print syntax error

I am experimenting with Hilbert curves written in Python in an Xcode IDE. The code listing is:

# python code to run the hilbert curve pattern
# from
import sys, math

def hilbert(x0, y0, xi, xj, yi, yj, n):
if n <= 0:
X = x0 + (xi + yi)/2
Y = y0 + (xj + yj)/2

# Output the coordinates of the cv
print '%s %s 0' % (X, Y)
hilbert(x0, y0, yi/2, yj/2, xi/2, xj/2, n - 1)
hilbert(x0 + xi/2, y0 + xj/2, xi/2, xj/2, yi/2, yj/2, n - 1)
hilbert(x0 + xi/2 + yi/2, y0 + xj/2 + yj/2, xi/2, xj/2, yi/2, yj/2, n - 1)
hilbert(x0 + xi/2 + yi, y0 + xj/2 + yj, -yi/2,-yj/2,-xi/2,-xj/2, n - 1)

def main():
args = sys.stdin.readline()
# Remain the loop until the renderer releases the helper...
while args:
arg = args.split()
# Get the inputs
pixels = float(arg[0])
ctype = arg[1]
reps = int(arg[2])
width = float(arg[3])

# Calculate the number of curve cv's
cvs = int(math.pow(4, reps))

# Begin the RenderMan curve statement
print 'Basis \"b-spline\" 1 \"b-spline\" 1'
print 'Curves \"%s\" [%s] \"nonperiodic\" \"P\" [' % (ctype, cvs)

# Create the curve
hilbert(0.0, 0.0, 1.0, 0.0, 0.0, 1.0, reps)

# End the curve statement
print '] \"constantwidth\" [%s]' % width

# Tell the renderer we have finished

# read the next set of inputs
args = sys.stdin.readline()
if __name__ == "__main__":

I am getting the following error from Xcode:
File "/Users/248239j/Desktop/hilbert/", line 12
print '%s %s' % (X, Y)
SyntaxError: invalid syntax

Would anyone have an alternative to that code line. Thanks in advance. I started using python today.

Answer Source

That's a problem with different Python-Versions.
Seems like this code was written for Python2.x but you're trying to run it with Python3.x.

The solution is to either use 2to3 to change these small differences automatically:

2to3 /Users/248239j/Desktop/hilbert/

Or manually replace the occurences of print <string> with print(<string>) (see Print is a function for more explanations).

Or just install Python2.x and run the code with that Python-Version

python2 /Users/248239j/Desktop/hilbert/
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