如何计算列表中符合特定条件的项目的百分比？

Question

I am making a program that looks at a file with data for hail in the US I have successfully created a class with objects (All the states), and have the state abbreviation, number of total hail reports, and list of hail sizes for each state/object.

I have to make a table showing statistics of the hail sizes for each state. I created a method that averages the hail sizes for each state, but I can't figure out how to make a method that calculates the percentages of hail sizes that fall within a certain size range.

The table has 5 categories, for these hail sizes: <1.25, 1.25-1.99, 2.0-2.49, 2.5-2.99, >3.0.
I am pretty sure I need to do a rolling sum for each category, but I just can't figure out how to do it with so many categories. If I could do a rolling sum, it would just be that sum/ the total number of reports for that state.

Here is the code I have so far:

 class stateHail: def __init__(self, state): self.stateAbbr = state self.hailReports = 0 self.hailSize = [] def avgSize(self): self.avg = (sum(self.hailSize))/self.hailReports #def percents(self): #??? #Creates objects needed for class states = [] for x in ["AL", "AK", "AZ", "AR", "CA", "CO", "CT", "DE", "FL", "GA", "HI", "ID", "IL", "IN", "IA", "KS", "KY", "LA", "ME", "MD", "MA", "MI", "MN", "MS", "MO", "MT", "NE", "NV", "NH", "NJ", "NM", "NY", "NC", "ND", "OH", "OK", "OR", "PA", "RI", "SC", "SD", "TN", "TX", "UT", "VA", "WA", "WV", "WI", "WY", "PR", "VA", "VI"]: stateObject = stateHail(x) states.append(stateObject) #Opens file and assigns state abbreviation, hail report number, and list of hail sizes to each object/state fileHail = open("90-99_hail.csv", "r") try: for line in fileHail: splitLine=line.split(",") abbrFile=splitLine[7] for x in states: if (abbrFile==x.stateAbbr): x.hailSize.append(float(splitLine[10])) x.hailReports = x.hailReports + 1 except: fileHail.close() #Calculates average for each state for x in states: if (x.hailReports>100): x.avgSize() print x.avg 

Answer 1

If I understand your question correctly, then you can store the percentages of each range in a list. The code may look something as follows

    self.percentages = [(self.hailSize[i]/self.hailReports) * 100 for i in range(5)]

Answer 2

If you have a list of hail sizes like this: [1.1,1.1,1.6,1.6,2.1,2.6,3.1,3.1,3.1]

you can get a list like this: [2, 2, 1, 1, 3]

from this:

return [len([item for item in self.hailSize if small<=item<big]) for small,big in [(0,1.25), (1.25,2), (2,2.5), (2.5,3), (3,200)]]

By the way, instead of saving a self.hailReports variable to count how many elements there are in self.hailSize , you can just use len(self.hailSize) . Next, have avgSize() simply do return sum(self.hailSize)/len(self.hailSize) , and then you don't have to call a function to update a variable all the time - just get the average size with avgSize() .