''' Python 3 code. scipy.mgrid is a useful! This short implementation comes without installing numpy. Supports complex step. "3j" means "three equi-spaced numbers from the span including the ends". >>> print(mgrid[1:2:3j]) [1.0, 1.5, 2.0] Supports floating point step. >>> print(mgrid[1:2:0.5]) [1.0, 1.5] does not support multi-dimensions, indicated by a tuple to scipy.mgrid >>> print(mgrid[1:2,3:5]) Traceback (most recent call last): File "p.py", line 16, in __getitem__ start,stop,step = s.start,s.stop,s.step AttributeError: 'tuple' object has no attribute 'start' During handling of the above exception, another exception occurred: Traceback (most recent call last): File "", line 1, in File "p.py", line 18, in __getitem__ raise TypeError('expected a slice') TypeError: expected a slice Deviates from scipy.mgrid. >>> mgrid[2:-1] # scipy.mgrid returns an empty list. [2, 1, 0] ''' def convert_slice_to_list(Slice,list_length): ''' A fun idiom. This gets python to deal with the "None" in slices like slice(None,None,3) ''' return list(range(list_length))[Slice] class poor_man_1D_mgrid: ''' grid()[slice] emulates the scipy mgrid function for vectors. ''' def __getitem__(self,s): try: start,stop,step = s.start,s.stop,s.step except: raise TypeError('expected a slice') start = start or 0 step = step or 1 L = stop-start if isinstance(step,complex): intervals = max(int(0.5+abs(step)),2) step = L/(intervals-1) halfway = start+L/2 l,r = [],[] for i in range(int(intervals/2)): delta = step*i r.append(stop-delta) l.append(start+delta) if intervals & 1: l.append(l[-1]+(r[-1]-l[-1])/2) l.extend(reversed(r)) return l if (L < 0) and (step == 1): step = -1 if step*L < 0: raise ValueError('avoid infinite list') return [start+step*i for i in range(max(int(0.5+L/step),1))] mgrid = poor_man_1D_mgrid()