Python Program help with IF Else

[ilikepython]

I also like the tuple (humble beginnings of a true object) to define a "course".
I do not, however, find any redeeming qualities in this usage:

grades[string.lowercase.index(grade.lower())]

Sorry, my friend:

• too many functions squished into one line (there is no advantage in doing so)

I'm not entirely convinced. I know its messy, but I think it could be made easier:
[code=python]
grade_names = ["a", "b", "c", "d", "f"]
grade_values = [4.0, 3.0, 2.0, 1.0, 0.0]

...

grade = grade.lower()
if grade not in grade_names:
print "Invalid Grade"
else:
value_index = grade_names.ind ex(grade)
totalpoints += grade_values[value_index] * credit
[/code]
The reason I used it was because it aviods writing the if statements. Also, it might be easier implementing it with classes:
[code=python]
grade_names = ["a", "b", "c", "d", "f"]
grade_values = [4.0, 3.0, 2.0, 1.0, 0.0]

class Grade:
value = 0.0
name = "f"

def setGrade(self, gr):
if type(gr) == type(0.0):
if gr in grade_values:
self.name = grade_names[grade_values.in dex(gr)]
self.value = gr

else:
print "Bad Grade"

elif type(gr) == type(''):
if gr in grade_names:
self.name = gr
self.value = grade_values[grade_names.ind ex(gr)]

else:
print "Bad Grade"
else:
print "Bad grade format"

def getGrade(self):
return self.name

def getValue(self):
return self.value

gr = Grade()
gr.setGrade(use r_input)

totalpoints += gr.getValue() * credit
[/code]
The class might not be the best, but it works as an example. Is this ok to do it like that?