DataFrame数据修改和算术运算

import numpy as np 
import pandas as pd

df = pd.DataFrame([['zs', 12], ['ls', 4]], columns = ['Name','Age']) 
df

df2 = pd.DataFrame([['ww', 16], ['zl', 8]], columns = ['Name','Age']) 
df2

df = df.append(df2)

df['Name'][0] = 'Tom' 
print(df)

  Name  Age
0  Tom   12
1   ls    4
0  Tom   16
1   zl    8
E:\ProgramData\Anaconda3\lib\site-packages\ipykernel_launcher.py:1: SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame
See the caveats in the documentation: https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy
  """Entry point for launching an IPython kernel.

s = pd.Series(range(5))
s

0    0
1    1
2    2
3    3
4    4
dtype: int64

s.where(s > 0,other=100)

0    100
1      1
2      2
3      3
4      4
dtype: int64

 s.mask(s>0,other=100)    #与where相反

0      0
1    100
2    100
3    100
4    100
dtype: int64

df = pd.DataFrame({'A': range(1, 6),
                   'B': range(10, 0, -2),
                   'C C': range(10, 5, -1)})
df

df.query('A > B')

df[df.A > df.B]

算术运算

df = pd.DataFrame(np.random.randn(8, 3), columns=list('ABC'))
df

df*5 + 2      #触发广播机制

1/df