如何在python中迭代数据帧,然后返回行值?
我有一个这样的数据框如何在python中迭代数据帧,然后返回行值?,python,pandas,loops,dataframe,Python,Pandas,Loops,Dataframe,我有一个这样的数据框 import pandas as pd d = {'col1': ["2004-02-26", "2004-02-27", "2004-03-01", "2004-03-02", "2004-03-03", "2004-03-04", "2004-03-05", "2004-03-08", "2004-03-09", "2004-03-10", "2004-03-11", "2004-03-
import pandas as pd
d = {'col1': ["2004-02-26", "2004-02-27", "2004-03-01",
"2004-03-02", "2004-03-03", "2004-03-04",
"2004-03-05", "2004-03-08", "2004-03-09",
"2004-03-10", "2004-03-11", "2004-03-12"],
'col2': [-3, 4, 5, 3, -1, 11, 123, 43, -5, 3, -4, -7],
'col3': [0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0,]}
df = pd.DataFrame(data=d)
print(df)
打印出来
col1 col2 col3
0 2004-02-26 -3 0
1 2004-02-27 4 1
2 2004-03-01 5 0
3 2004-03-02 3 0
4 2004-03-03 -1 1
5 2004-03-04 11 0
6 2004-03-05 123 0
7 2004-03-08 43 0
8 2004-03-09 -5 0
9 2004-03-10 3 1
10 2004-03-11 -4 1
11 2004-03-12 -7 0
您可以在df['col2']
中看到,正值由两个负值分隔。我想选择每组正值的首行和尾行,以创建一个新的数据帧。如果只有一个正行留在中间的话,我假设头和尾是相同的。< /P>
比如说,
head_date col2h co3h tail_date col2t col3t
2004-02-27 4 1 2004-03-02 3 0
2004-03-04 11 0 2004-03-08 43 0
2004-03-10 3 1 2004-03-10 3 1
我在想,当col20的第(I)行返回I+1行值时,以及当col2的第(I)行>0和col2的第(I+1)行时,选择这些行
df1 = df.loc[(df['col2'].shift() < 0) & (df['col2'] > 0)].copy()
df1.rename(columns = {'col1': 'head_date', 'col2': 'col2h', 'col3': 'col3h'}, inplace = True)
df2 = df.loc[(df['col2'].shift(-1) < 0) & (df['col2'] > 0)].copy()
df2.rename(columns = {'col1': 'head_date', 'col2': 'col2t', 'col3': 'col3t'})
new_df = pd.concat([df1.reset_index(drop = True), df2.reset_index(drop = True)], axis = 1)
head_date col2h col3h head_date col2t col3t
0 2004-02-27 4 1 2004-03-02 3 0
1 2004-03-04 11 0 2004-03-08 43 0
2 2004-03-10 3 1 2004-03-10 3 1