-1, 0]])
>>> b = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
a[a==0]=b[a==0]
矩阵乘法
np.dot
pandas的交集、并集...、补集、leftjoin等:
1.场景,对于colums都相同的dataframe做过滤的时候
例如:
df1 = DataFrame([[‘a‘, 10, ‘男‘],...columns=[‘name‘, ‘age‘, ‘sex‘])
取交集:print(pd.merge(df1,df2,on=[‘name‘, ‘age‘, ‘sex‘]))
取并集...:print(pd.merge(df1,df2,on=[‘name‘, ‘age‘, ‘sex‘], how=‘outer‘))
取差集(从df1中过滤df1在df2中存在的行):
df1 = df1....df1.append(df2)
df1 = df1.drop_duplicates(subset=[‘name‘, ‘age‘, ‘sex‘],keep=False)
print(df1)
Pandas groupy