Pandas

Question

这是我的代码：

import pandas as pd
df = pd.DataFrame(columns = ["A", "B"])
df.iloc[0]['A'] = 5

这是输出：

Traceback (most recent call last):
  File "K:/Dop/Pentas/Simpletest/Temp.py", line 38, in <module>
    df.iloc[0]['A'] = 5
  File "C:\Python34\lib\site-packages\pandas\core\indexing.py", line 1189, in __getitem__
    return self._getitem_axis(key, axis=0)
  File "C:\Python34\lib\site-packages\pandas\core\indexing.py", line 1480, in _getitem_axis
    return self._get_loc(key, axis=axis)
  File "C:\Python34\lib\site-packages\pandas\core\indexing.py", line 89, in _get_loc
    return self.obj._ixs(key, axis=axis)
  File "C:\Python34\lib\site-packages\pandas\core\frame.py", line 1719, in _ixs
    label = self.index[i]
  File "C:\Python34\lib\site-packages\pandas\core\index.py", line 1076, in __getitem__
    return getitem(key)
IndexError: index 0 is out of bounds for axis 0 with size 0

关于如何修复它有什么建议吗？我事先不知道我的数据框的整体大小，但我可以猜到。

Answer 1

您可以使用

使用数据初始化数据框

df = pd.DataFrame(columns=["A", "B"], data=[[5,np.nan]]),

或使用 set_value 方法（顺便说一下，这比 iloc 快得多）： df.set_value(0,'A',5)

更新 2018-04-12⬇

因为 pandas 版本 0.21.0 df.set_value 已弃用。您应该改用 .at[] 或 .iat[] 访问器：

df.at[0, 'A'] = 5

Answer 2

提供动态增加数据框的示例...sizeOfDataFrame 变量仅限制将数据添加到数据框并且是动态的循环...

import pandas as pd
import numpy as np
yourDataFrame = pd.DataFrame()
sizeOfDataFrame = np.random.randint(100, size=1)
for currentLine in range(sizeOfDataFrame):
    yourDataFrame = yourDataFrame.append(pd.DataFrame({"A":np.random.randint(100, size=1),"B":np.random.randint(100, size=1),"C":np.random.randint(100, size=1)},index=[0]))
yourDataFrame.reset_index(inplace = True)    
yourDataFrame.drop('index',axis=1,inplace=True)

Pandas - 手动创建数据框并插入值

Pandas - create dataframe manually and insert values

manual

dataframe