Question

在下面找到从excel文件计算每个城市中的订阅者，客户和其他客户总数的代码，并计算他们在每个城市的平均旅行时间。有没有办法在下面的代码中简化for循环中的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

我推荐Pandas dataframes这样的事情。您可以根据另一列中的值轻松地对数据框进行子集化，并对值进行求和，计算数字等。以下是如何将此问题应用于您的问题的示例：

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

一种选择是使用这样的列表推导：

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'])

有没有办法在下面的代码中简化for循环中的If，elif语句？

2 个答案: