从python中的文件进行计算

Question

我有一份文件，里面有学校代码和对不同城市的投票。

该文件如下：

City: California
ADS, 532
SJD, 221
WPE, 239
City: Chicago
ADS, 238
SJD, 233
WPE, 456
...

我的问题是

1. 如何向文件中添加信息？比方说，我想把DJF加到芝加哥，我该怎么做呢？

1. 如何计算每个学校代码的总票数？芝加哥和加州的WPE？

我试着用字典使它更容易，但我感到迷茫。此外，我设置了将新信息添加到文件中的代码，但我希望将其添加到特定的类别中，而不仅仅是在文件的末尾。

我是个初学者，所以我仍有很多事情要处理。

Answer 1

欢迎来到这里！为了实现您想要的结果，您基本上可以创建一个带有键和值对的嵌套字典。然后，您可以访问第一级键，并在文件中添加其他信息，如芝加哥的DJF。然后，您可以将该字典作为json对象写入文件。要得到和，基本上可以使用和函数。以下是代码：

import json
dictForCities ={"California" : {"ADS" : 532, "SJD": 221, "WPE" : 239 }, "Chicago": {"ADS": 238, "SJD": 233, "WPE": 456}}
dictForCities["Chicago"]["DJF"] = 204
with open('test', 'w') as f:
    f.write(json.dumps(dictForCities))


# To get the total of votes 
sumForADS = sum(d['ADS'] for d in dictForCities.values() if d)
sumForWPE = sum(d['WPE'] for d in dictForCities.values() if d)
print(sumForADS)
print(sumForWPE)

希望这能有所帮助！

Answer 2

# start of temporary file read

data = '''City: California
ADS, 532
SJD, 221
WPE, 239
City: Chicago
ADS, 238
SJD, 233
WPE, 456'''

# change it to your file read method, e.g.:
# with open('data.txt','r') as f:
#     data = f.read()
#     ...
import tempfile
with tempfile.TemporaryFile(mode='w+') as fp:
    fp.write(data)
    fp.seek(0)
    data = fp.read()
# end of temporary file read
    
    lines = data.split('\n')
    cities = dict()
    last_city = None
    for line in lines: # you can use `for line in f:` if your file is big
        line = line.strip() # remove leading and trailing spaces
        if line.startswith('City:'): # is this line a city's name?
            last_city = line.removeprefix('City: ') # then save it without the `City: ` part
        elif last_city is not None: # do we have any city saved?
            name, value = line.split(',') # split line into a list: `ADS, 532` -> ['ADS', ' 532'], note the extra space before 532
            name = name.strip() # remove spaces
            value = int(value.strip()) # remove spaces and convert to integer
            values = cities.setdefault(last_city,dict()) # get the dictionary at key `last_city` or return a new one if it doesn't exist yet
            values[name] = value # add value to this dictionary, this is the same as the `cities[last_city]' so it will get added here too
            
# now we have our data structure filled with data from the file

# function to print cities
def print_cities(cities):
    for city,values in cities.items():
        print(city)
        for name,value in values.items():
            print(f'\t{name}: {value}')
    print('-'*16) # separator
    
#let's print it
print_cities(cities)

# add a new value to it
cities['Chicago']['DJF'] = 204

# let's print again, note that the DJF, 204 got added to Chicago
print_cities(cities)
        
# write to file
with open('output.txt','w') as f:
    for city,values in cities.items():
        f.write(f'City: {city}\n')
        for name,value in values.items():
            f.write(f'{name}, {value}\n')

我试着解释每一行，我还添加了一个临时文件读，这是你不需要的，但由于我没有你的文件，也不知道它是什么样子，我复制了顶部的内容，并试图模仿一个文件读取。您可以用普通的文件读取来交换该部分，我也添加了该文件。

您需要将文件读入数据结构，修改其内容，然后将其写入文件。