背景我刚刚将我的 Pandas 从 0.11 升级到 0.13.0rc1。现在，应用程序弹出许多新警告。其中一个是这样的：E:\FinReporter\FM_EXT.py:449: SettingWithCopyWarning: A va...
我刚刚将我的 Pandas 从 0.11 升级到 0.13.0rc1。现在，应用程序弹出许多新警告。其中一个是这样的：
E:\FinReporter\FM_EXT.py:449: SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_index,col_indexer] = value instead
quote_df['TVol'] = quote_df['TVol']/TVOL_SCALE
我想知道这到底是什么意思？我需要做些更改吗？
如果我坚持使用，该如何取消警告 quote_df['TVol'] = quote_df['TVol']/TVOL_SCALE ？
def _decode_stock_quote(list_of_150_stk_str):
"""decode the webpage and return dataframe"""
from cStringIO import StringIO
str_of_all = "".join(list_of_150_stk_str)
quote_df = pd.read_csv(StringIO(str_of_all), sep=',', names=list('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefg')) #dtype={'A': object, 'B': object, 'C': np.float64}
quote_df.rename(columns={'A':'STK', 'B':'TOpen', 'C':'TPCLOSE', 'D':'TPrice', 'E':'THigh', 'F':'TLow', 'I':'TVol', 'J':'TAmt', 'e':'TDate', 'f':'TTime'}, inplace=True)
quote_df = quote_df.ix[:,[0,3,2,1,4,5,8,9,30,31]]
quote_df['TClose'] = quote_df['TPrice']
quote_df['RT'] = 100 * (quote_df['TPrice']/quote_df['TPCLOSE'] - 1)
quote_df['TVol'] = quote_df['TVol']/TVOL_SCALE
quote_df['TAmt'] = quote_df['TAmt']/TAMT_SCALE
quote_df['STK_ID'] = quote_df['STK'].str.slice(13,19)
quote_df['STK_Name'] = quote_df['STK'].str.slice(21,30)#.decode('gb2312')
quote_df['TDate'] = quote_df.TDate.map(lambda x: x[0:4]+x[5:7]+x[8:10])
return quote_df
E:\FinReporter\FM_EXT.py:449: SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_index,col_indexer] = value instead
quote_df['TVol'] = quote_df['TVol']/TVOL_SCALE
E:\FinReporter\FM_EXT.py:450: SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_index,col_indexer] = value instead
quote_df['TAmt'] = quote_df['TAmt']/TAMT_SCALE
E:\FinReporter\FM_EXT.py:453: SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_index,col_indexer] = value instead
quote_df['TDate'] = quote_df.TDate.map(lambda x: x[0:4]+x[5:7]+x[8:10])
创建 SettingWithCopyWarning 的目的是标记可能令人困惑的“链式”分配，例如以下内容，它并不总是按预期工作，特别是当第一个选择返回副本时 。 [ 有关背景讨论， and 和 GH5597
df[df['A'] > 2]['B'] = new_val # new_val not set in df
该警告建议重写如下：
df.loc[df['A'] > 2, 'B'] = new_val
但是，这不符合你的用法，这相当于：
df = df[df['A'] > 2]
df['B'] = new_val
虽然很明显您并不关心写入是否返回到原始框架（因为您正在覆盖对它的引用），但不幸的是，此模式无法与第一个链式分配示例区分开来。因此出现了（误报）警告。 索引文档 。您可以使用以下分配安全地禁用此新警告。
import pandas as pd
pd.options.mode.chained_assignment = None # default='warn'