[Tutor] Strange list behaviour in classes

[James Reynolds]

Thank you! I think I have working in the right direction. I have one more
question related to this module.

I had to move everything to a single module, but what I would like to do is
have this class in a file by itself so I can call this from other modules.
when it was in separate modules it ran with all 0's in the output.

Here is the code in one module:

#import Statistics

class Statistics:
def __init__(self, *value_list):
self.value = value_list
self.square_list= []
 def mean(self, *value_list):
try :
ave = sum(self.value) / len(self.value)
except ZeroDivisionError:
ave = 0
return ave

def median(self, *value_list):
if len(self.value) <= 2:
n = self.mean(self.value)
elif len(self.value) % 2 == 1:
m = (len(self.value) - 1)/2
n = self.value[m+1]
else:
m = len(self.value) / 2
m = int(m)
n = (self.value[m-1] + self.value[m]) / 2
return n
 def variance(self, *value_list):
average = self.mean(*self.value)
for n in range(len(self.value)):
square = (self.value[n] - average)**2
self.square_list.append(square)
try:
var = sum(self.square_list) / len(self.square_list)
except ZeroDivisionError:
var = 0
return var

def stdev(self, *value_list):
var = self.variance(*self.value)
sdev = var**(1/2)
return sdev
 def zscore(self, x, *value_list):
average = self.mean(self.value)
sdev = self.stdev(self.value)
try:
z = (x - average) / sdev
except ZeroDivisionError:
z = 0
return z



a = [1,2,3,4,5,6,7,8,9,10]
stats = Statistics(*a)
mean = stats.mean(*a)
median = stats.median(*a)
var = stats.variance(*a)
stdev = stats.stdev(*a)
z = stats.zscore(5, *a)
print(mean, median, var, stdev, z)
print()



On Wed, Feb 24, 2010 at 7:33 PM, Alan Gauld <alan.gauld at btinternet.com>wrote:

>
> "James Reynolds" <eire1130 at gmail.com> wrote
>
>  I understand, but if self.value is any number other then 0, then the "for"
>> will append to the square list, in which case square_list will always have
>> some len greater than 0 when "value" is greater than 0?
>>
>
> And if value does equal zero?
>
> Actually I'm confused by value because you treat it as both an
> integer and a collection in different places?
>
>
>  Is this an occasion which is best suited for a try:, except statement? Or
>> should it, in general, but checked with "if's". Which is more expensive?
>>
>
> try/except is the Python way :-)
>
>
>  def variance(self, *value_list):
>>   if self.value == 0:
>>        var = 0
>>   else:
>>         average = self.mean(*self.value)
>>         for n in range(len(self.value)):
>>              square = (self.value[n] - average)**2
>>              self.square_list.append(square)
>>    var = sum(self.square_list) / len(self.square_list)
>>    return var
>>
>
>
> --
> Alan Gauld
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
>
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