Pandas 查询使用筛选和排序，导致未解决的错误

Question

我正在为文档字符串中概述的编码 class 解决这个问题。我将不胜感激任何关于优化我的代码的帮助以及关于为什么尽管重置了索引我仍收到以下错误的任何解释。

import pandas as pd
def beds_top_ten(df, facility_id):
    '''
    INPUT: DataFrame, int
    OUTPUT: date
    Write a pandas query that returns the ten census dates with the highest 
    number of available beds for the nursing home with the specified facility id
    REQUIREMENTS:
    Do a filter followed by a sort rather than a sort followed by a merge.
    '''
    df = pd.read_csv('beds.csv', low_memory= False)
    df['Bed Census Date'] = pd.to_datetime(df['Bed Census Date'])
    df = df.filter(items =['Facility ID', 'Bed Census Date','Available Residential Beds'])
    df = df.sort_values(by =[ 'Facility ID', 'Available Residential Beds'], ascending= False)
    df_group_by_ten = df.groupby('Facility ID').head(10).reset_index(drop=True)
    dates = df_group_by_ten.loc[df_group_by_ten['Facility ID']==facility_id, 'Bed Census Date']
    return dates

这是 table 在第一个 groupby 之后的样子：

Facility ID Bed Census Date Available Residential Beds
336 19  2011-01-05  29
339 19  2010-12-15  28
330 19  2011-02-23  27
332 19  2011-02-02  27
333 19  2011-01-26  27
334 19  2011-01-19  27
335 19  2011-01-12  27
338 19  2010-12-22  27
341 19  2010-12-01  27
331 19  2011-02-09  26
16  17  2013-04-10  22
87  17  2011-11-09  19
30  17  2013-01-02  17
37  17  2012-11-07  17
47  17  2012-08-29  17
31  17  2012-12-26  16
56  17  2012-06-20  16
10  17  2013-05-22  15
27  17  2013-01-23  15
61  17  2012-05-16  15

当我运行来自我的 command_line 时：

In [15]: beds_top_ten('beds.csv',17)
Out[15]:
16   2013-04-10
87   2011-11-09
30   2013-01-02
37   2012-11-07
47   2012-08-29
31   2012-12-26
56   2012-06-20
10   2013-05-22
27   2013-01-23
61   2012-05-16
Name: Bed Census Date, dtype: datetime64[ns]

然而当我运行在线环境中使用相同的代码时，出现以下错误：

/usr/local/lib/python2.7/unittest/suite.py:108: DtypeWarning: Columns (10,45) have mixed types. Specify dtype option on import or set low_memory=False.
  test(result)
E
======================================================================
ERROR: test_fourth_pandas (test_methods.Test)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/src/app/test_methods.py", line 25, in test_fourth_pandas
    all_equal = np.all(result == answer)
  File "/usr/local/lib/python2.7/site-packages/pandas/core/ops.py", line 812, in wrapper
    raise ValueError(msg)
ValueError: Can only compare identically-labeled Series objects

----------------------------------------------------------------------
Ran 1 test in 19.743s

FAILED (errors=1)

Answer 1

删除日期格式行解决了上述错误。

 df = pd.read_csv('beds.csv', low_memory= False)
    #df['Bed Census Date'] = pd.to_datetime(df['Bed Census Date'])
    df = df.filter(items=['Facility ID', 'Bed Census Date','Available Residential Beds'])
    x = df[df['Facility ID'] == facility_id].sort_values('Available Residential Beds', ascending=False).head(10)
    return x['Bed Census Date']

Answer 2

pd.to_datetime没问题。您可能有错误的日期。尝试指定格式，然后 errors='coerce 将无效格式转换为 NaT.

df['Bed Census Date'] = pd.to_datetime(df['Bed Census Date'].str.strip(), 
                            format='%Y-%m-%d', errors='coerce')

现在，扩展我的，使用 head 过滤、排序并获取前 10 个项目：

x = df[df['Facility ID'] == facility_id]\
      .sort_values('Available Residential Beds', ascending=False).head(10)
return x['Bed Census Date']

Pandas 查询使用筛选和排序，导致未解决的错误

Pandas query using filter and sort, leading to unresolved errors

python

error-handling

pandas

pandas-groupby