from numpy.core.defchararray import index
import pandas as pd
import numpy as np
s=pd.Series([1,2,3,4,np.nan,44])
print(s)
dates=pd.date_range('20210603',periods=6)
print(dates)
df=pd.DataFrame(np.random.randn(6,4),index=dates,columns=['a','b','c','d'])
print(df)
df1=pd.DataFrame(np.arange(12).reshape((3,4)))
print(df1)
df2=pd.DataFrame({'A':1.,'B':pd.Timestamp('20130102'),'C':pd.Series(1,index=list(range(4)),dtype='float32'),'D':np.array([3]*4,dtype='int32'),'E':pd.Categorical(["test","train","test","train"]),'F':'food'})
print('df2 is:\n',df2)
print(df2.dtypes)
print(df2.index)
print(df2.columns)
print(df2.values)
print('des\n',df2.describe())
print(df2.T)
print(df2.sort_index(axis=0,ascending=False))
print(df2.sort_values(by='E')) #sort by specific value like SQL