提问人：SChatcha 提问时间：11/12/2023 更新时间：11/12/2023 访问量：46
根据另一列中的条件填写列中的值
Fill in the value in the column based on the condition in another column
问：
我有数据帧。
data={"ID":[1,1,1,1,1,1,1,1,1,2,2,2],
"Year":[2000,2001,2002,2003,2004,1997,1998,2003,2004,1997,1998,2005],
"Firm":["A","A","B","B","A","A","A","A","B","B","A","A"],
"Count":[0,1,0,0,0,0,0,0,0,0,0,0]}
df1=pd.DataFrame(data)
预期的输出是这样的。
data={"ID":[1,1,1,1,1,1,1,1,1,2,2,2],
"Year":[2000,2001,2002,2003,2004,1997,1998,2003,2004,1997,1998,2005],
"Firm":["A","A","B","B","A","A","A","A","B","B","A","A"],
"Count":[0,1,0,0,0,0,0,0,0,0,0,0],
"Count_1":[0,1,1,1,1,0,0,1,1,0,0,0]}
df2=pd.DataFrame(data)
我可以通过我的代码实现预期的输出。
df_1=df1.sort_values(by=["ID","Year"],ascending=True)
df_1["Count_1"]=np.where(df_1["Count"]==1,1,np.NaN)
df_1["Count_1"]=df_1.groupby(["ID"],as_index=None)["Count_1"].ffill()
df_1.drop(columns=["Count"],inplace=True)
df_1.fillna(0)
但是，我正在寻找更短、更干净的代码。
答：
1赞
Andrej Kesely
11/12/2023
#1
尝试：
df1 = df1.sort_values(by=["ID", "Year"])
df1["Count_1"] = (df1.groupby("ID")["Count"].cumsum() > 0).astype(int)
print(df1)
指纹：
ID Year Firm Count Count_1
5 1 1997 A 0 0
6 1 1998 A 0 0
0 1 2000 A 0 0
1 1 2001 A 1 1
2 1 2002 B 0 1
3 1 2003 B 0 1
7 1 2003 A 0 1
4 1 2004 A 0 1
8 1 2004 B 0 1
9 2 1997 B 0 0
10 2 1998 A 0 0
11 2 2005 A 0 0
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