weather.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
        
"""计算各大城市温差最大的月份            
@author:linyi   
"""             
from __future__ import division 
from sys import argv

city_month={}
result={}
        
script, file_name = argv
file = open(file_name)
for lines in file: 
        line = lines.rstrip('\n').split()
        ## year >= 1996
        if(int(line[1][:4]) < 1996):
                continue
        ## key = city + year + month
        key = line[0] + "-" + line[1][:7]
        ## difference in temperature    
        diff = int(line[2][4:]) - int(line[3][4:])
        ## value = [diff sum,days]      
        value = city_month.get(key)
        if(value):
                value[0] = value[0] + diff
                value[1] = value[1] + 1
        else:
                value = {}
                value[0] = diff
                value[1] = 1
                city_month[key] = value
file.close()

## get the max
for key,value in city_month.items():
        city = key[0:-8]
        avg = value[0]/value[1]
        tmp = result.get(city)
        if(not tmp or tmp[1] < avg):
                max = {}
                max[0] = key
                max[1] = avg
                result[city] = max
        ## record the days with same avg
        elif(tmp and tmp[1]==avg):
                tmp[0] = tmp[0] + " " +key[-7:]

## out result           
for key,value in result.items():
        print key,
        print value[0][value[0].index('-')+1:],
        print value[1]