another class difining question

[python101]

I would like to write a program for calculating the distance of an from initial distance x0 and to a distance vot
distance = x0 + v0t

Here is my "intended" code
[code=python]
class distance:
def __init__(self, iniX, iniV):
self._x0= iniX
self._v0= iniV

def setTime(self,t) :
self._t0=t

def result(self):
return self._x0 + self._v0*t

#the result I would like to have
d = distance(5,10)
d.setTime(5)
#d = 5 + 10*5 = 55
>>>55
d.setTime(5)
#d=d(5) [the first distance set by t=5] + vo*5[the new distance set by another t=5]=105
>>>105
[/code]
How can I write the right code?

[bartonc]

I would like to write a program for calculating the distance of an from initial distance x0 and to a distance vot
distance = x0 + v0t

Here is my "intended" code
[code=python]
class distance:
def __init__(self, iniX, iniV):
self._x0= iniX
self._v0= iniV

def setTime(self,t) :
self._t0=t

def result(self):
return self._x0 + self._v0*t

#the result I would like to have
d = distance(5,10)
d.setTime(5)
#d = 5 + 10*5 = 20
>>>20
d.setTime(5)
#d=d(5) [the first distance set by t=5] + d(5)[the new distance set by another t=5]=40
>>>40
[/code]
How can I write the right code?

Here's where you initially when wrong: self._v0*t t exists in the set function only. You save a copy for other functions to use (self._t0), so use that.[CODE=python]
class distance:
def __init__(self, iniX, iniV):
self._x0= iniX
self._v0= iniV
self._t0 = 1

def __str__(self):
return "%f" %self.result()

def setTime(self,t) :
self._t0 = t

def result(self):
return self._x0 + (self._v0 * self._t0)


d = distance(5, 10)
print d
d.setTime(5)
print d[/CODE]

[python101]

Since 5 + (10 * 5) will never equal 20, I can't be sure about your math, but here's where you initially when wrong: self._v0*t t exists in the set function only. You save a copy for other functions to use (self._t0), so use that.[CODE=python]
class distance:
def __init__(self, iniX, iniV):
self._x0= iniX
self._v0= iniV
self._t0 = 1

def __str__(self):
return "%f" %self.result()

def setTime(self,t) :
self._t0 = t

def result(self):
return self._x0 + (self._v0 * self._t0)


d = distance(5, 10)
print d
d.setTime(5)
print d[/CODE]

Thank you for helping me.

In your code,

[code=python]
def __str__(self):
return "%f" %self.result()[/code]
the result(), we haven't defined yet. when I try , the distance can't be updated; still 55, if enter setTime(5) several times.

It should be 105 if I enter setTime(5) 2 times, 155 if enter setTime(5) 3 times. In other words, it continues add v0*t into the previous distance

[bartonc]

Thank you for helping me.

[code=python]
class distance:
def __init__(self, iniX, iniV):
self._x0= iniX
self._v0= iniV

def __str__(self):
return "%f" %self.result()

def setTime(self, t):
self._x0 += self._v0 * t

def result(self):
return self._x0


d = distance(5, 10)
print d
d.setTime(5)
print d
d.setTime(5)
print d[/CODE]5.000000
55.000000
105.000000

If you use better (more descriptive) names for your variable, then it will be easier for those of us that are reading your code to be able to help. Remember, all this is your creation and none of us as been thinking along these same lines.