我有2个数据帧。第一个数据帧包含年份和计数为0：
year count
0 1890 0
1 1891 0
2 1892 0
3 1893 0
4 1894 0
5 1895 0
6 1896 0
7 1897 0
8 1898 0
9 1899 0
10 1900 0
11 1901 0
12 1902 0
13 1903 0
14 1904 0
15 1905 0
16 1906 0
17 1907 0
18 1908 0
19 1909 0
20 1910 0
21 1911 0
22 1912 0
23 1913 0
24 1914 0
25 1915 0
26 1916 0
27 1917 0
28 1918 0
29 1919 0
.. ... ...
90 1980 0
91 1981 0
92 1982 0
93 1983 0
94 1984 0
95 1985 0
96 1986 0
97 1987 0
98 1988 0
99 1989 0
100 1990 0
101 1991 0
102 1992 0
103 1993 0
104 1994 0
105 1995 0
106 1996 0
107 1997 0
108 1998 0
109 1999 0
110 2000 0
111 2001 0
112 2002 0
113 2003 0
114 2004 0
115 2005 0
116 2006 0
117 2007 0
118 2008 0
119 2009 0
[120 rows x 2 columns]
第二个数据框具有相似的列，但填充的年数较少且填充计数：
year count
0 1970 1
1 1957 7
2 1947 19
3 1987 12
4 1979 7
5 1940 1
6 1950 19
7 1972 4
8 1954 15
9 1976 15
10 2006 3
11 1963 16
12 1980 6
13 1956 13
14 1967 5
15 1893 1
16 1985 5
17 1964 6
18 1949 11
19 1945 15
20 1948 16
21 1959 16
22 1958 12
23 1929 1
24 1965 12
25 1969 15
26 1946 12
27 1961 1
28 1988 1
29 1918 1
30 1999 3
31 1986 3
32 1981 2
33 1960 2
34 1974 4
35 1953 9
36 1968 11
37 1916 2
38 1955 5
39 1978 1
40 2003 1
41 1982 4
42 1984 3
43 1966 4
44 1983 3
45 1962 3
46 1952 4
47 1992 2
48 1973 4
49 1993 10
50 1975 2
51 1900 1
52 1991 1
53 1907 1
54 1977 4
55 1908 1
56 1998 2
57 1997 3
58 1895 1
我想创建第三个数据帧df3。对于每一行，如果df1和df2中的年份相等，则df3 [“count”] = df2 [“count”]否则df3 [“count”] = df1 [“count”]。我尝试使用join来执行此操作：
df_new = df2.join(df1, on='year', how='left')
df_new['count'] = df_new['count'].fillna(0)
print(df_new)
但是得到了一个错误：
ValueError: columns overlap but no suffix specified: Index(['year'], dtype='object')
我找到了这个错误的解决方案（Pandas join issue: columns overlap but no suffix specified）但是在我运行带有这些更改的代码之后：
df_new = df2.join(df1, on='year', how='left', lsuffix='_left', rsuffix='_right')
df_new['count'] = df_new['count'].fillna(0)
print(df_new)
但输出不是我想要的：
count year
0 NaN 1890
1 NaN 1891
2 NaN 1892
3 NaN 1893
4 NaN 1894
5 NaN 1895
6 NaN 1896
7 NaN 1897
8 NaN 1898
9 NaN 1899
10 NaN 1900
11 NaN 1901
12 NaN 1902
13 NaN 1903
14 NaN 1904
15 NaN 1905
16 NaN 1906
17 NaN 1907
18 NaN 1908
19 NaN 1909
20 NaN 1910
21 NaN 1911
22 NaN 1912
23 NaN 1913
24 NaN 1914
25 NaN 1915
26 NaN 1916
27 NaN 1917
28 NaN 1918
29 NaN 1919
.. ... ...
29 1.0 1918
30 3.0 1999
31 3.0 1986
32 2.0 1981
33 2.0 1960
34 4.0 1974
35 9.0 1953
36 11.0 1968
37 2.0 1916
38 5.0 1955
39 1.0 1978
40 1.0 2003
41 4.0 1982
42 3.0 1984
43 4.0 1966
44 3.0 1983
45 3.0 1962
46 4.0 1952
47 2.0 1992
48 4.0 1973
49 10.0 1993
50 2.0 1975
51 1.0 1900
52 1.0 1991
53 1.0 1907
54 4.0 1977
55 1.0 1908
56 2.0 1998
57 3.0 1997
58 1.0 1895
[179 rows x 2 columns]
期望的输出是：
year count
0 1890 0
1 1891 0
2 1892 0
3 1893 1
4 1894 0
5 1895 1
6 1896 0
7 1897 0
8 1898 0
9 1899 0
10 1900 1
11 1901 0
12 1902 0
13 1903 0
14 1904 0
15 1905 0
16 1906 0
17 1907 1
18 1908 1
19 1909 0
20 1910 0
21 1911 0
22 1912 0
23 1913 0
24 1914 0
25 1915 0
26 1916 2
27 1917 0
28 1918 1
29 1919 0
.. ... ...
90 1980 6
91 1981 2
92 1982 4
93 1983 3
94 1984 3
95 1985 5
96 1986 3
97 1987 12
98 1988 1
99 1989 0
100 1990 0
101 1991 1
102 1992 2
103 1993 10
104 1994 0
105 1995 0
106 1996 0
107 1997 3
108 1998 2
109 1999 3
110 2000 0
111 2001 0
112 2002 0
113 2003 1
114 2004 0
115 2005 0
116 2006 3
117 2007 0
118 2008 0
119 2009 0
[120 rows x 2 columns]
因为你应该把year作为索引的问题。此外，如果您不想丢失数据，则应加入outer而不是left。
这是我的代码：
df = pd.DataFrame({
"year" : np.random.randint(1850, 2000, size=(100,)),
"qty" : np.random.randint(0, 10, size=(100,)),
})
df2 = pd.DataFrame({
"year" : np.random.randint(1850, 2000, size=(100,)),
"qty" : np.random.randint(0, 10, size=(100,)),
})
df = df.set_index("year")
df2 = df2.set_index("year")
df3 = df.join(df2["qty"], how = "outer", lsuffix='_left', rsuffix='_right')
df3 = df3.fillna(0)
在此步骤中，您有2列，其值为df1或df2。在你合并规则中，我没有得到你想要的。你说 ：
- 如果df1 [“qty”] == df2 [“qty”] => df3 [“qty”] = df2 [“qty”]
- 如果df1 [“qty”]！= df2 [“qty”] => df3 [“qty”] = df1 [“qty”]
这意味着你每次都需要qazxsw poi因为qazxsw poi。我对吗 ？
以防万一。如果您想要调整代码，可以使用df1["qty"]如下：
df1["qty"] == df2["qty"]我希望它有所帮助，
萨科