Question

I know this is a common question but I could not find the solution for my case. I have gotten a problem while a for-loop in Python. When I run a program with this piece

for j in range(len(line1)- 3):
    print 'j =', j
    spl1 = spline(line1[j], line1[j + 1], line1[j + 2], line1[j + 3], t, Nu)

print 'spl1 ='
matrix.show(spl1)

i get an output:

Traceback (most recent call last):
File "D:\work\curvature\test\twisted\cardinal_spline.py", line 272, in <module> main()
File "D:\work\curvature\test\twisted\cardinal_spline.py", line 111, in main 
matrix.show(spl1)
UnboundLocalError: local variable 'spl1' referenced before assignment

Moreover, it does not print j-variable. I cannot see any mistake there. The “spl1” is assigned in the for-loop but it looks like the interpreter just skips it.

please point on the mistake.

Answer 1

Your for-loop doesn’t get executed at all due to len(line1) <= 3 in some cases, so spl1 isn’t assigned.