How about this (edit if vector/point.py):
def _pdict_lists(self, other, num):
"""Creates a list of lists from self to other using _pos_dict. """
outlist = [[self]]
oldlist = [[]]
while outlist != oldlist:
oldlist = outlist[:]
for i, v in enumerate(outlist):
templist = v[-1]._pdlist[num].keys()
for i2, v2 in enumerate(templist):
if not v.__contains__(v2):
littletemplist = v + [v2]
if not outlist.__contains__(littletemplist):
outlist.append(littletemplist)
for i, v in enumerate(oldlist):
if v[-1] != other:
outlist.remove(v)
outlist.sort(key=len)
if len(outlist) != 0:
return outlist
raise ValueError('No Connecting Path found between ' + other.name +
' and ' + self.name)
def _pdict_list(self, other, num):
"""Creates a list from self to other using _pos_dict. """
return self._pdict_lists(other, num)[0]
def pos_from(self, otherpoint, singleframe=False, frame=None, variables=False):
"""Returns a Vector distance between this Point and the other Point.
Parameters
==========
otherpoint : Point
The otherpoint we are locating this one relative to
singleframe : boolean
Expresses the resulting vector in a single frame
frame : ReferenceFrame
Expresses the resulting vector in this frame
variables : boolean
If True, the coordinate symbols(if present) in the resulting Vector
are re-expressed in terms the resulting frame (if singleframe is True
or frame is given)
Examples
========
>>> from sympy.physics.vector import Point, ReferenceFrame
>>> N = ReferenceFrame('N')
>>> p1 = Point('p1')
>>> p2 = Point('p2')
>>> p1.set_pos(p2, 10 * N.x)
>>> p1.pos_from(p2)
10*N.x
"""
if frame is not None:
_check_frame(frame)
last_error = None
plists = self._pdict_lists(otherpoint, 0)
for plist in plists:
outvec = Vector(0)
for i in range(len(plist) - 1):
outvec += plist[i]._pos_dict[plist[i + 1]]
# 0 Vector
if len(outvec.args) == 0:
return outvec
try:
if frame is not None:
# Express in the given frame
outvec = outvec.express(frame, variables=variables)
elif singleframe:
# Express in a single frame
outvec = outvec.express(outvec.args[0][1], variables=variables)
return outvec
except ValueError as e:
last_error = e
continue
raise last_error
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