有什么方法可以简化下面代码中for循环内的If，elif语句？

Question

在代码下面找到代码，该代码可从excel文件计算每个城市的订户，客户和其他客户的总数，并计算每个城市的平均旅行时间。 有什么方法可以简化下面代码中for循环内的If，elif语句？

new_file = {'Washington': './data/Washington-2016-Summary.csv',
         'Chicago': './data/Chicago-2016-Summary.csv',
         'NYC': './data/NYC-2016-Summary.csv'}

for city, filename in new_file.items():

    with open (filename, 'r') as fil_1:
    t_subscriber = 0
    t_customers = 0
    cnt_subscribers = 0
    cnt_customers = 0
    other_customers = 0
    file_reader = csv.DictReader(fil_1)

    for row in data_reader:
        if row['user_type'] == 'Subscriber':
            cnt_subscribers += 1
            t_subscribers += float(row['duration'])
        elif row['user_type'] == 'Customer':
            cnt_customers += 1
            t_customers += float(row['duration'])
        elif row['user_type'] == '':
            other_customers += 1
            t_customers += float(row['duration'])

    tripaverage_duration = (t_subscribers+t_customers)/60)/(cnt_subscribers+cnt_customers+other_customers)
    tripaverage_subscribers = (t_subscribers/60)/cnt_subscribers
    tripaverage_subscribers = (t_customers/60)/cnt_customers

    print ('Average trip duration in', city,'-' 
    ,tripaverage_duration,'minutes')
    print ('Average trip duration for subscribers in', city,'-' 
    ,tripaverage_subscribers,'minutes')
    print ('Average trip duration for customers in', city,'-' 
    ,tripaverage_subscribers,'minutes')
    print ('\n')

Answer 1

我建议使用类似这样的Pandas数据框 。 您可以轻松地根据另一列中的值对数据框进行子集，并对值求和，对数字进行计数等。这是如何将其应用于问题的示例：

import pandas as pd    
new_file = {'Washington': './data/Washington-2016-Summary.csv',
             'Chicago': './data/Chicago-2016-Summary.csv',
             'NYC': './data/NYC-2016-Summary.csv'}

for city, filename in new_file.items():

    data = pd.read_csv(filename)
    tripaverage_duration = data.values.mean()['duration']
    tripaverage_subscribers = data[data['user_type']=='Subscriber'].values.mean()['duration']
    tripaverage_customers = data[data['user_type']=='Customer'].values.mean()['duration']


print ('Average trip duration in', city,'-' 
    ,tripaverage_duration,'minutes')
    print ('Average trip duration for subscribers in', city,'-' 
    ,tripaverage_subscribers,'minutes')
    print ('Average trip duration for customers in', city,'-' 
    ,tripaverage_subscribers,'minutes')
    print ('\n')

Answer 2

一种选择是使用像这样的列表理解：

cnt_subscribers = sum([1 for row in data_reader if row['user_type'] == 'Subscriber'])
t_subscribers = sum([float(row['duration']) for row in data_reader if row['user_type'] == 'Subscriber'])