在pandas中合并循环中的多个系列

所以我有一个系列的清单如下:

groupdf1
Out[304]: 
[90-95    9
 >100     1
 80-90    1
 50-80    1
 Name: bucket, dtype: int64, 80-90     9
 95-100    1
 90-95     1
 50-80     1
 Name: bucket, dtype: int64, 80-90    10
 90-95     1
 50-80     1
 Name: bucket, dtype: int64, 80-90     11
 95-100     1
 Name: bucket, dtype: int64, 50-80    9

我尝试的是创建一个如下所示的数据帧:

      bucket.1  bucket.2 bucket.3 bucket.4
90-95   9         1         1        NaN
>100    1        NaN       NaN       NaN
80-90   1         9        10        11
50-80   1         1         1        NaN
95-100 NaN       NaN       NaN        1

groupdf=pd.DataFrame(groupdf1[0])
for i in range(1,len(groupdf1)):
    groupdf2=pd.DataFrame(groupdf1[i])
    groupdf.concat(groupdf2)


Traceback (most recent call last):

  File "<ipython-input-278-4c8876ecdb74>", line 4, in <module>
    groupdf.concat(groupdf2)

  File "C:\Users\hp1\Anaconda3\lib\site-packages\pandas\core\generic.py", line 3081, in __getattr__
    return object.__getattribute__(self, name)

AttributeError: 'DataFrame' object has no attribute 'concat'

有人能帮帮我吗?谢谢。