齿隙误差. pandas 使用动态查询字符串过滤数据帧. [英] Backlash error. Pandas filter dataframe using dynamic query string.

问题描述

大家好， 该问题与Python反冲错误有关. 我正在创建用于过滤大熊猫的动态查询字符串. 代码是:

Hi all, The problem is related to the Python backlash error. I am creating a dynamic query string for filtering in pandas. The code is:

       filters = dict(wlbWellType=['EXPLORATION'])
       query_string = ''
       index = 0
       for (k,v) in filters.iteritems():
          for i in v:
              if (index == 0):
                  query_string += '"{}"'.format((k) + ' == '+"'{}'".format(i)) 
              else:
              query_string += ' & ' '"{}"'.format((k) + ' == ' + 
              "'{}'".format(i))
             index += 1

如果我执行"print query_string"，则输出为

If I do "print query_string" the output I got is

             "wlbWellType == 'EXPLORATION'"

如果我执行"query_string"，则输出为

If I do "query_string" the output I got is

             '"wlbWellType == \'EXPLORATION\'"'

我想要

             "wlbWellType == 'EXPLORATION'" 

作为输出而不使用print语句.似乎存在与反冲有关的错误.

as the output without using print statement. Seems there is an error related to backlash.

query_string输出将用作:

The query_string output will then be used as:

            df.query(query_string)

有人可以帮我解决上述问题吗?

Can anyone please help me with the above problem?

预先感谢

推荐答案

您可以编写自己的帮助器函数(类似于您现在正在尝试的功能，但使用了**kwargs)并使用@varname语法作为价值占位符.

You can write your own helper function (similar to what you're trying now but making use of **kwargs) and use the @varname syntax as the value placeholder.

def my_filter(df, **kwargs):
    qs = ' & '.join('{0} == @{0}'.format(k) for k in kwargs)
    return df.query(qs, local_dict=kwargs)

然后使用如下:

new_df = my_filter(df, wlbWellType='EXPLORATION', otherColumn='SOMETHING')

此方法比手动转义值更安全，因为@varname语法会根据值的类型为您做适当的选择.

This method is safer than manually escaping values as the @varname syntax will do that appropriately for you depending on the value's type.

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