pandas

pandas的基础是numpy

• 两者可以试试相互转
• dataframe转化成numpy.ndarray

  df=df.values
  

• numpy.ndarray转化成dataframe

  df = pd.DataFrame(df)
  

关系

• DataFrame是Series的容器，Panel是DataFrame的容器 DataFrame用得最多

对比

• pandas.Series( data, index, dtype, copy)

• pandas.DataFrame( data, index, columns, dtype, copy)

• 参考文档

pandas stack和unstack

• 图形直观说明 stack_unstack_todict.png
• 代码说明

  import numpy as np
  import pandas as pd
  from pandas import Series,DataFrame
  data=DataFrame(np.arange(6).reshape((2,3)),index=pd.Index(['street1','street2']),columns=pd.Index(['one','two','three']))
  print(data)
  print('-----------------------------------------\n')
  print(data.to_dict())
  print('-----------------------------------------\n')
  data2=data.stack()
  data3=data2.unstack()
  print(data2)
  print('-----------------------------------------\n')
  print(data3)
  

• 返回结果 返回结果.png

groupby使用

• 代码说明

  df = pd.DataFrame({'key1':['a','a','b','b','a'],'key2':['one','two','one','two','one'],'data1':np.random.randn(5),'data2':np.random.randn(5)})
  means = df['data1'].groupby([df['key1'], df['key2']]).sum()
  means.unstack()
  

• 返回 DF.png STACK.png TO_DICT.png