python - 如何在 Python 中迭代类对象并更改属性值
问题描述
我有以下两个类 MasterProgramList 和 ProgramList。MasterProgramList 接受一个 json 数组对象,该对象在下面的使用代码中定义。我正在尝试遍历每个 Program 对象并更改 start_date 属性。当我这样做时,该值不会改变,而是保持在 json 数组对象中定义的值。我的 ProgramList/Program 类有问题吗?如何迭代类对象并更改属性值?
主程序列表.py
import json
import datetime
class MasterProgramList(object):
def __init__(self, program_list, today=None):
self.program_list = [ProgramList(program) for program in program_list]
self.today = today
def current_programs(self):
if self.today is not None:
def filter_if_between_start_and_end(program):
return (datetime.datetime.strptime(program.start_date, '%Y-%m-%d').date()) <= self.today.date() <= (
datetime.datetime.strptime(program.end_date, '%Y-%m-%d').date())
program_list = self.program_list
for x in program_list:
x.programs = filter(filter_if_between_start_and_end, x.programs)
filtered_program_list = program_list
else:
filtered_program_list = self.program_list
return filtered_program_list
程序列表.py
class ProgramList(object):
"""
CRM-specific version of the ProgramList Configuration object
"""
def __init__(self, config):
self._config = config
self.brand = config['brand']
self.programs = self._parse_programs(config['brand'], config['programs'])
def _parse_programs(cls, brand, program_list):
return [Program.from_json(brand, p) for p in program_list]
class Program(object):
def __init__(self, **kwargs):
self._config = kwargs.get('config') #required json data
self.name = kwargs.get('name') #required json data
self.start_date = kwargs.get('start_date') #required json data
self.end_date = kwargs.get('end_date') #required json data
def __repr__(self):
return str(self._config)
@classmethod
def from_json(cls, brand, program_json):
program_json['name'] = '{0}_{1}'.format(brand.capitalize(), program_json['name'])
program_json['department'] = 'CRM'
return Program(
config = program_json,
name = program_json['name'],
start_date = program_json['start_date'],
end_date = program_json['end_date']
)
用法:
from datetime import datetime, timedelta
crm_program_master_list = [
{
"brand": "testbrand",
"programs": [
{
"name": "Program1",
"start_date": "2020-01-02",
"end_date": "2999-12-31"
},
{
"name": "Program2",
"start_date": "2020-01-04",
"end_date": "2999-12-31"
}
]
}
]
today_date = (datetime.strptime('2020-01-06', '%Y-%m-%d'))
crm_programs_to_analyze = MasterProgramList(crm_program_master_list, today=today_date)
crm_programs_to_analyze.program_list = crm_programs_to_analyze.current_programs()
programs = []
for x in crm_programs_to_analyze.program_list:
for p in x.programs:
#change the start_date for each program
p.start_date = '2020-01-22'
print('program: {}'.format(p))
programs.append(p)
output:
program: {'name': 'Program1', 'end_date': '2999-12-31', 'department': 'CRM', 'start_date': '2020-01-02'}
program: {'name': 'Program2', 'end_date': '2999-12-31', 'department': 'CRM', 'start_date': '2020-01-04'}
expected output:
program: {'name': 'Program1', 'end_date': '2999-12-31', 'department': 'CRM', 'start_date': '2020-01-22'}
program: {'name': 'Program2', 'end_date': '2999-12-31', 'department': 'CRM', 'start_date': '2020-01-22'}
解决方案
首先,需要清理一些东西才能使这项工作:
在 Usage 部分,没有ProgramList
or的导入MasterProgramList
。我将它们添加为:
from MasterProgramList import MasterProgramList
from ProgramList import ProgramList
然后,在MasterProgramList.py
我添加了一个ProgramList
.
继续前进,我看到这crm_programs_to_analyze.program_list
是一个包含一个ProgramList.ProgramList
对象的列表。因此,您的外部for
循环在该单个对象上迭代一次。然后内部for
循环遍历ProgramList
's 程序的成员,并将其设置start_date
为2020-01-22
。
您遇到的问题出在方法中__repr__
- 特别是它获取返回值的地方。这是一个非常简短的示例来说明问题:
>>> class f:
... def __init__(self, config):
... self.config = config
... self.start_date = config['start_date']
... self.end_date = config['end_date']
... def __repr__(self):
... return str(self.config)
...
>>> conf = {'start_date': '2020-10-10', 'end_date': '2021-12-03'}
>>> foo = f(conf)
>>> foo
{'start_date': '2020-10-10', 'end_date': '2021-12-03'}
>>> foo.start_date = '2019-10-10' # <-- Changes start_date, but not config
>>> foo
{'start_date': '2020-10-10', 'end_date': '2021-12-03'} # <-- From config
>>> foo.start_date # <-- but this as updated as expected
'2019-10-10'
>>> foo.config
{'start_date': '2020-10-10', 'end_date': '2021-12-03'} # <-- unchanged
>>> foo.config['start_date'] = foo.start_date
>>> foo
{'start_date': '2019-10-10', 'end_date': '2021-12-03'}
>>> foo.start_date
'2019-10-10'
>>> foo.config # <-- now it's changed and they match
{'start_date': '2019-10-10', 'end_date': '2021-12-03'}
的值start_date
正在更新。p
但是通过打印__repr__
是从 获取原始值_config
,修改时不会更新p.start_date
。要修复它,要么添加更新以更改start_date
in p._config
,要么__repr__
返回值 of start_date
。
像这样:
def __repr__(self):
rv = f'Start Date: {self.start_date}, End Date: {self.end_date}, Config: '
for k, v in self._config.items():
rv += f'{k} : {v}, '
return rv
推荐阅读
- jquery - 如何创建一个 td 对象 jquery
- javascript - 这个解析器扩展功能是如何工作的?
- django - Django:从表 group_by 状态中选择状态,计数(状态);
- r - 5折交叉验证
- java - 为私有方法编写 NullPointerException 的 junit 测试用例时出现问题
- cmake - 在 CLion 中使用 SDL2 时,进程以退出代码 -1073741515 (0xC0000135) 完成
- python - 循环遍历列表以创建多个 excel 文件
- java - 不影响返回的条件的突变测试
- mysql - 存储过程,使用变量无结果
- postgresql - postgresql 中的 NOLOGIN 用户有什么用?