使用函数和条件向数据框中添加新列

Question

我使用了下面的代码；

def my_function(price_label):
    for index, line in df.iterrows():
        if df['Price'] <= 15000:
            return "Low"
        elif df['Price'] > 15000 and df['Price'] <= 38000:
            return "Average"
        elif df['Price'] > 38000:
            return "High"

# Add a new column 'Price Status' based on values from other columns
df['Price Label'] = df['Price'].apply(my_function)
df

我收到此错误消息；

Traceback (most recent call last):
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\IPython\core\interactiveshell.py", line 3553, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "C:\Users\boni\AppData\Local\Temp\ipykernel_22476\186094663.py", line 11, in <module>
    df['Price Status'] = df['Price'].apply(my_function)
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\pandas\core\series.py", line 4904, in apply
    ).apply()
      ^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\pandas\core\apply.py", line 1427, in apply
    return self.apply_standard()
           ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\pandas\core\apply.py", line 1507, in apply_standard
    mapped = obj._map_values(
             ^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\pandas\core\base.py", line 921, in _map_values
    return algorithms.map_array(arr, mapper, na_action=na_action, convert=convert)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\pandas\core\algorithms.py", line 1743, in map_array
    return lib.map_infer(values, mapper, convert=convert)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "lib.pyx", line 2972, in pandas._libs.lib.map_infer
  File "C:\Users\boni\AppData\Local\Temp\ipykernel_22476\186094663.py", line 3, in my_function
    if df['Price'] <= 15000:
       ^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\pandas\core\generic.py", line 1576, in __nonzero__
    raise ValueError(
ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\IPython\core\interactiveshell.py", line 2144, in showtraceback
    stb = self.InteractiveTB.structured_traceback(
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\IPython\core\ultratb.py", line 1448, in structured_traceback
    return FormattedTB.structured_traceback(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\IPython\core\ultratb.py", line 1339, in structured_traceback
    return VerboseTB.structured_traceback(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\IPython\core\ultratb.py", line 1186, in structured_traceback
    formatted_exception = self.format_exception_as_a_whole(etype, evalue, etb, number_of_lines_of_context,
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\IPython\core\ultratb.py", line 1076, in format_exception_as_a_whole
    self.get_records(etb, number_of_lines_of_context, tb_offset) if etb else []
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\IPython\core\ultratb.py", line 1168, in get_records
    FrameInfo(
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\site-packages\IPython\core\ultratb.py", line 780, in __init__
    ix = inspect.getsourcelines(frame)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\inspect.py", line 1264, in getsourcelines
    lines, lnum = findsource(object)
                  ^^^^^^^^^^^^^^^^^^
  File "C:\Users\boni\AppData\Local\Programs\Python\Python312\Lib\inspect.py", line 1093, in findsource
    raise OSError('could not get source code')
OSError: could not get source code

这可能是什么原因造成的？

Answer 1

你无法通过

df['price']

。以下是如何执行此操作：

def my_function(price_label):
    if price_label <= 15000:
        return "Low"
    elif 15000 < price_label <= 38000:
        return "Average"
    else:
        return "High"

import pandas as pd

data = {
    'Price': [10000, 20000, 40000, 12000, 35000]
}
df = pd.DataFrame(data)

df['Price Label'] = df['Price'].apply(my_function)
print(df)

这给出了

   Price Price Label
0  10000         Low
1  20000     Average
2  40000        High
3  12000         Low
4  35000     Average