为什么我的PyMongo查询中出现无效错误

Question

我正在编写一个pymongo查询，当我在MongoDB GUI中编写该查询时它可以工作，但始终收到SyntaxError: invalid syntax错误。

我究竟做错了什么？

def get_codes(request):
   get_code = newsCode.aggregate([{
    '$match': {
        'site': { 
            '$exists': true 
        },
        'segment': {
            '$exists': true
        }
   }, {
    '$group': {
        '_id': {
            'site': "$site",
            'seg_code': {
                '$substr': ["$segment", 0, 4]
            },
            'segment': "$segment"
        }
    }
   }, {
    '$project': {
        'site': "$_id.site",
        'seg_code': "$_id.seg_code",
        'segment': "$_id.segment"
    }
   }, {
    '$sort': {
        '_id': 1
    }
   }
  }])

我的错误是显示在,附近

 }, {
  '$project

追溯：

Traceback (most recent call last):
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/site-packages/django/utils/autoreload.py", line 225, in wrapper
fn(*args, **kwargs)
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 120, in inner_run
self.check(display_num_errors=True)
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/site-packages/django/core/management/base.py", line 364, in check
include_deployment_checks=include_deployment_checks,
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/site-packages/django/core/management/base.py", line 351, in _run_checks
return checks.run_checks(**kwargs)
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/site-packages/django/core/checks/registry.py", line 73, in run_checks
new_errors = check(app_configs=app_configs)
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/site-packages/django/core/checks/urls.py", line 40, in check_url_namespaces_unique
all_namespaces = _load_all_namespaces(resolver)
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/site-packages/django/core/checks/urls.py", line 57, in _load_all_namespaces
url_patterns = getattr(resolver, 'url_patterns', [])
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/site-packages/django/utils/functional.py", line 36, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/site-packages/django/urls/resolvers.py", line 540, in url_patterns
patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/site-packages/django/utils/functional.py", line 36, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/site-packages/django/urls/resolvers.py", line 533, in urlconf_module
return import_module(self.urlconf_name)
File "/Users/userName/anaconda3/envs/env_dp_36/lib/python3.6/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 978, in _gcd_import
File "<frozen importlib._bootstrap>", line 961, in _find_and_load
File "<frozen importlib._bootstrap>", line 950, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 655, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 678, in exec_module
File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed
File "/Users/userName/Desktop/Dash/dash/dash/urls.py", line 3, in <module>
from . import views
File "/Users/userName/Desktop/Dash/dash/dash/views.py", line 5, in <module>
from .datamanager import *
File "/Users/userName/Desktop/Dash/dash/dash/datamanager.py", line 471
}, {
 ^
SyntaxError: invalid syntax

为什么会出现此错误？ 就像我说的那样，当我在GUI中执行此操作时，它就起作用了。 我的语法有问题吗？ PyMongo代码是否应该与MongoDB代码不同？

请帮忙！

Answer 1

欢迎来到StackOverflow！

这里发生了几件事情：

1）使用pymongo时，您是用python编写的，因此true必须更改为True

2）当您尝试将这些查询聚合在一起时，aggregation函数接受代表查询一部分的字典列表。 您发布的代码片段将一个列表传递到函数中，其中第一个条目是包含$match和$group键的部分，但是$project键发生在该字典被上一行的大括号括起来之后。 我不确定为什么在pymongo shell中不会引发错误，因为肯定存在括号不匹配的情况，mongo对此都不满意。

我清理了以下代码段中的括号对齐方式，但不确定在应用程序上下文中运行查询时是否还会出现其他问题。

def get_codes(request):
    get_code = newsCode.aggregate([
        {'$match': {'site': {'$exists': true}, 'segment': {'$exists': true}}},
        {'$group': {
            '_id': {
                'site': "$site",
                'seg_code': {'$substr': ["$segment", 0, 4]},
                'segment': "$segment"
            },
        }},
        {'$project': {
            'site': "$_id.site",
            'seg_code': "$_id.seg_code",
            'segment': "$_id.segment"
        }},
        {'$sort': {'_id': 1}},
    ])

最后一点：pymongo中的排序与编写原始mongo查询时的排序不同。 参考： 如何使用pymongo对mongodb进行排序