'numpy.float64' object is not iterable

Question

I'm trying to iterate an array of values generated with numpy.linspace:

slX = numpy.linspace(obsvX, flightX, numSPts)
slY = np.linspace(obsvY, flightY, numSPts)

for index,point in slX:
    yPoint = slY[index]
    arcpy.AddMessage(yPoint)

This code worked fine on my office computer, but I sat down this morning to work from home on a different machine and this error came up:

File "C:\temp\gssm_arcpy.1.0.3.py", line 147, in AnalyzeSightLine
  for index,point in slX:
TypeError: 'numpy.float64' object is not iterable

slX is just an array of floats, and the script has no problem printing the contents -- just, apparently iterating through them. Any suggestions for what is causing it to break, and possible fixes?

Solution

numpy.linspace() gives you a one-dimensional NumPy array. For example:

>>> my_array = numpy.linspace(1, 10, 10)
>>> my_array
array([  1.,   2.,   3.,   4.,   5.,   6.,   7.,   8.,   9.,  10.])

Therefore:

for index,point in my_array

cannot work. You would need some kind of two-dimensional array with two elements in the second dimension:

>>> two_d = numpy.array([[1, 2], [4, 5]])
>>> two_d
array([[1, 2], [4, 5]])

Now you can do this:

>>> for x, y in two_d:
    print(x, y)

1 2
4 5

Comments

[Robert Kern]

One does not iterate over an array of floats with for index, point in slX:. This will not work in any version of Python with any version of numpy. Instead, did you actually run for index, point in enumerate(slX): on your office computer? That would seem to be what you are intending to accomplish.

[Erica]

Same versions of numpy, python, and Arc. I don't need to work in float64 and frankly didn't know I was until the error was thrown. Robert, as far as I know the code is exactly the same (I saved it in my Dropbox folder, however, so it's possible there was a sync error somewhere between there and here which means I'm working with an older version; the enumerate(slX) makes a lot more sense)

[MSIS]

Muller: Sorry for necropost. I am having a similar error message when defining variance: I already defined the mean, mean(Y). Now I set Def :Var(Y): y_bar=mean(Y)