Question

paid_students=[]
for students in enrollments:
    if students['days_to_cancel']==None or students['days_to_cancel']>7:
        paid_students.append(students)
print len(paid_students)

输出：

len(enrollments)的值也是1640。为什么所有行都会附加到paid_students list，即使注册中有很多行的['days_to_cancel']值范围很宽。

注册的示例数据

{u'account_key': u'448',
 u'cancel_date': u'2014-11-10',
 u'days_to_cancel': u'5',
 u'is_canceled': u'True',
 u'is_udacity': u'True',
 u'join_date': u'2014-11-05',
 u'status': u'canceled'}

{u'account_key': u'448',
 u'cancel_date': u'2015-01-27',
 u'days_to_cancel': u'0',
 u'is_canceled': u'True',
 u'is_udacity': u'True',
 u'join_date': u'2015-01-27',
 u'status': u'canceled'}

来源-Udacity

Answer 1

这对我有用：我在if的第二个参数中添加了一个int（），你在比较stings（你的dic值）和整数，在python 2中，如注释中指出的那样总是返回true。

enrollments= [{u'account_key': u'448', u'cancel_date': u'2014-11-10', u'days_to_cancel': u'5', u'is_canceled': u'True', u'is_udacity': u'True', u'join_date': u'2014-11-05', u'status': u'canceled'},
{u'account_key': u'448', u'cancel_date': u'2015-01-27', u'days_to_cancel': u'10', u'is_canceled': u'True', u'is_udacity': u'True', u'join_date': u'2015-01-27', u'status': u'canceled'}]

paid_students=[]
for students in enrollments:
    if students['days_to_cancel']==None or int(students['days_to_cancel'])>7:
        paid_students.append(students)

print len(paid_students)

为什么所有数据都会附加到列表

1 个答案: