Python 熊猫:依赖于其他值的列
我有一个熊猫数据框,如下所示:Python 熊猫:依赖于其他值的列,python,pandas,if-statement,conditional-statements,multiple-columns,Python,Pandas,If Statement,Conditional Statements,Multiple Columns,我有一个熊猫数据框,如下所示: col1 col2 col3 col4 0 5 1 11 9 1 2 3 14 7 2 6 5 54 8 3 11 2 67 44 4 23 8 2 23 5 1 5 9 8 6 9 7 45 71 我想创建一个第五列(col5),它依赖于col1的
col1 col2 col3 col4
0 5 1 11 9
1 2 3 14 7
2 6 5 54 8
3 11 2 67 44
4 23 8 2 23
5 1 5 9 8
6 9 7 45 71
我想创建一个第五列(col5),它依赖于col1的值,并取其他列中的一个值
这是我想要的样子,但我有一些问题
if col1 < 3:
col5 == col2
elif col1 < 7 & col1 >= 3:
col5 == col3
elif col1 >= 7 & col1 < 50:
col5 == col4
提前感谢,如果您有任何问题,请告诉我您可以使用多个,如果没有条件为True
(col1=>50
)已添加最后一个值1
:
df['col5'] = np.where(df['col1'] <3, df['col2'],
np.where((df['col1'] <7) & (df['col1'] >=3 ), df['col3'],
np.where((df['col1'] >=7) & (df['col1'] <50 ), df['col4'], 1)))
print (df)
col1 col2 col3 col4 col5
0 5 1 11 9 11
1 2 3 14 7 3
2 6 5 54 8 54
3 11 2 67 44 44
4 23 8 2 23 23
5 97 5 9 8 1
6 9 7 45 71 71
len(df)=7000中的计时:
In [441]: %timeit df['col51'] = np.where(df['col1'] <3, df['col2'], np.where((df['col1'] <7) & (df['col1'] >=3 ), df['col3'], df['col4']))
The slowest run took 5.31 times longer than the fastest. This could mean that an intermediate result is being cached.
1000 loops, best of 3: 1.25 ms per loop
In [442]: %timeit df["col52"] = df.apply(lambda x: col52(x), axis=1)
1 loop, best of 3: 552 ms per loop
In [443]: %timeit df["col53"] = [col53(c1,c2,c3,c4) for c1,c2,c3,c4 in zip(df.col1,df.col2,df.col3,df.col4)]
100 loops, best of 3: 9.87 ms per loop
计时代码:
#change 1000 to 10000 for 70k
df = pd.concat([df]*1000).reset_index(drop=True)
def col52(x):
if x["col1"] < 3:
return x["col2"]
elif x["col1"] >=3 and x["col1"] < 7:
return x["col3"]
elif x["col1"] >= 7 and x["col1"] < 50:
return x["col4"]
def col53(c1,c2,c3,c4):
if c1 < 3:
return c2
elif c1 >=3 and c1 < 7:
return c3
elif c1>= 7 and c1< 50:
return c4
df['col51'] = np.where(df['col1'] <3, df['col2'], np.where((df['col1'] <7) & (df['col1'] >=3 ), df['col3'], df['col4']))
df["col52"] = df.apply(lambda x: col52(x), axis=1)
df["col53"] = [col53(c1,c2,c3,c4) for c1,c2,c3,c4 in zip(df.col1,df.col2,df.col3,df.col4)]
print (df)
#将70k的1000更改为10000
df=pd.concat([df]*1000)。重置索引(drop=True)
def col52(x):
如果x[“col1”]<3:
返回x[“col2”]
elif x[“col1”]>=3和x[“col1”]<7:
返回x[“col3”]
elif x[“col1”]>=7和x[“col1”]<50:
返回x[“col4”]
def col53(c1、c2、c3、c4):
如果c1<3:
返回c2
如果c1>=3且c1<7:
返回c3
如果c1>=7且c1<50:
返回c4
df['col51']=np。其中(df['col1']一种方法是使用pd.DataFrame.apply函数:
def col5(x):
if x["col1"] < 3:
return x["col2"]
elif x["col1"] >=3 and x["col1"] < 7:
return x["col3"]
elif x["col1"] >= 7 and x["col1"] < 50:
return x["col4"]
另外,一般来说,apply可能非常慢,特别是当您有带有if-else块的函数时,因为对于每一行,您的处理器必须决定应执行if-else块中的哪个语句(“流水线”和“分支预测”)。不过你在这里应该没问题。是列数,逻辑是固定的吗?是的,列和逻辑是固定的。col1>50的逻辑是什么?
?太棒了!col52比col53慢得多是因为数据帧吗?列访问比行访问快得多吗?谢谢!
In [446]: %timeit df['col51'] = np.where(df['col1'] <3, df['col2'], np.where((df['col1'] <7) & (df['col1'] >=3 ), df['col3'], df['col4']))
100 loops, best of 3: 2.5 ms per loop
In [447]: %timeit df["col52"] = df.apply(lambda x: col52(x), axis=1)
1 loop, best of 3: 5.36 s per loop
In [448]: %timeit df["col53"] = [col53(c1,c2,c3,c4) for c1,c2,c3,c4 in zip(df.col1,df.col2,df.col3,df.col4)]
10 loops, best of 3: 96.3 ms per loop
#change 1000 to 10000 for 70k
df = pd.concat([df]*1000).reset_index(drop=True)
def col52(x):
if x["col1"] < 3:
return x["col2"]
elif x["col1"] >=3 and x["col1"] < 7:
return x["col3"]
elif x["col1"] >= 7 and x["col1"] < 50:
return x["col4"]
def col53(c1,c2,c3,c4):
if c1 < 3:
return c2
elif c1 >=3 and c1 < 7:
return c3
elif c1>= 7 and c1< 50:
return c4
df['col51'] = np.where(df['col1'] <3, df['col2'], np.where((df['col1'] <7) & (df['col1'] >=3 ), df['col3'], df['col4']))
df["col52"] = df.apply(lambda x: col52(x), axis=1)
df["col53"] = [col53(c1,c2,c3,c4) for c1,c2,c3,c4 in zip(df.col1,df.col2,df.col3,df.col4)]
print (df)
def col5(x):
if x["col1"] < 3:
return x["col2"]
elif x["col1"] >=3 and x["col1"] < 7:
return x["col3"]
elif x["col1"] >= 7 and x["col1"] < 50:
return x["col4"]
df["col5"] = df.apply(lambda x: col5(x), axis=1)