python-3.x - df.copy() 方法不支持的操作数类型

Question

我正在上传我的数据集，我正在复制我的数据集，但出现错误。

import numpy as np
import pandas as pd
import mathplotlib.pyplot as plt

house_data=pd.read_csv("/home/houseprice.csv")

#we evaluate the price of a house for those cases where the information is missing, for each variable
def analyse_na_value(df, var):
    df - df.copy()
    
    # we indicate as a variable as 1 where the observation is missing
    # we indicate as 0 where the observation has a real value
    df[var] = np.where(df[var].isnull(), 1 , 0)
    #print(df[var].isnull())
    
    # we calculate the mean saleprice where the information is missing or present
    df.groupby(var)['SalePrice'].median().plot.bar()
    plt.title(var)
    plt.show()
    
    
for var in vars_with_na:
    analyse_na_value(house_data, var)

错误，当我注释此代码行时，我没有收到错误消息

df - df.copy()

TypeError                                 Traceback (most recent call last)
~/anaconda3/lib/python3.8/site-packages/pandas/core/ops/array_ops.py in na_arithmetic_op(left, right, op, is_cmp)
    142     try:
--> 143         result = expressions.evaluate(op, left, right)
    144     except TypeError:

~/anaconda3/lib/python3.8/site-packages/pandas/core/computation/expressions.py in evaluate(op, a, b, use_numexpr)
    232         if use_numexpr:
--> 233             return _evaluate(op, op_str, a, b)  # type: ignore
    234     return _evaluate_standard(op, op_str, a, b)

~/anaconda3/lib/python3.8/site-packages/pandas/core/computation/expressions.py in _evaluate_numexpr(op, op_str, a, b)
    118     if result is None:
--> 119         result = _evaluate_standard(op, op_str, a, b)
    120 

~/anaconda3/lib/python3.8/site-packages/pandas/core/computation/expressions.py in _evaluate_standard(op, op_str, a, b)
     67     with np.errstate(all="ignore"):
---> 68         return op(a, b)
     69 

TypeError: unsupported operand type(s) for -: 'str' and 'str'

During handling of the above exception, another exception occurred:

TypeError                                 Traceback (most recent call last)
<ipython-input-31-25d58bc46c86> in <module>
     15 
     16 for var in vars_with_na:
---> 17     analyse_na_value(house_data, var)

<ipython-input-31-25d58bc46c86> in analyse_na_value(df, var)
      1 #we evaluate the price of a house for those cases where the information is missing, for each variable
      2 def analyse_na_value(df, var):
----> 3     df - df.copy()
      4 
      5     # we indicate as a variable as 1 where the observation is missing

~/anaconda3/lib/python3.8/site-packages/pandas/core/ops/__init__.py in f(self, other, axis, level, fill_value)
    649         if isinstance(other, ABCDataFrame):
    650             # Another DataFrame
--> 651             new_data = self._combine_frame(other, na_op, fill_value)
    652 
    653         elif isinstance(other, ABCSeries):

~/anaconda3/lib/python3.8/site-packages/pandas/core/frame.py in _combine_frame(self, other, func, fill_value)
   5864                 return func(left, right)
   5865 
-> 5866         new_data = ops.dispatch_to_series(self, other, _arith_op)
   5867         return new_data
   5868 

~/anaconda3/lib/python3.8/site-packages/pandas/core/ops/__init__.py in dispatch_to_series(left, right, func, axis)
    273         #  _frame_arith_method_with_reindex
    274 
--> 275         bm = left._mgr.operate_blockwise(right._mgr, array_op)
    276         return type(left)(bm)
    277 

~/anaconda3/lib/python3.8/site-packages/pandas/core/internals/managers.py in operate_blockwise(self, other, array_op)
    362         Apply array_op blockwise with another (aligned) BlockManager.
    363         """
--> 364         return operate_blockwise(self, other, array_op)
    365 
    366     def apply(self: T, f, align_keys=None, **kwargs) -> T:

~/anaconda3/lib/python3.8/site-packages/pandas/core/internals/ops.py in operate_blockwise(left, right, array_op)
     36             lvals, rvals = _get_same_shape_values(blk, rblk, left_ea, right_ea)
     37 
---> 38             res_values = array_op(lvals, rvals)
     39             if left_ea and not right_ea and hasattr(res_values, "reshape"):
     40                 res_values = res_values.reshape(1, -1)

~/anaconda3/lib/python3.8/site-packages/pandas/core/ops/array_ops.py in arithmetic_op(left, right, op)
    188     else:
    189         with np.errstate(all="ignore"):
--> 190             res_values = na_arithmetic_op(lvalues, rvalues, op)
    191 
    192     return res_values

~/anaconda3/lib/python3.8/site-packages/pandas/core/ops/array_ops.py in na_arithmetic_op(left, right, op, is_cmp)
    148             #  will handle complex numbers incorrectly, see GH#32047
    149             raise
--> 150         result = masked_arith_op(left, right, op)
    151 
    152     if is_cmp and (is_scalar(result) or result is NotImplemented):

~/anaconda3/lib/python3.8/site-packages/pandas/core/ops/array_ops.py in masked_arith_op(x, y, op)
     90         if mask.any():
     91             with np.errstate(all="ignore"):
---> 92                 result[mask] = op(xrav[mask], yrav[mask])
     93 
     94     else:

TypeError: unsupported operand type(s) for -: 'str' and 'str'

1

据我所知，copy() 函数适用于 python3，
但在 pandas ,
我不知道 python3 是否有效。
如何在不注释该代码行的情况下摆脱此错误？

Answer 1

我认为你应该做 df = df.copy() .不过，我建议更改变量。 Here是有关此功能的官方 Pandas 文档。您正在做的是从自身减去数据框...