How to create column for my csv file in python
You can use Pandas for this, your file format isn't exactly comma separated values file. But still you can us pandas read_csv() method.
Suppose you're file name is test_file

import pandas as pd
df = pd.read_csv('test_file', sep=':', header=None)
&gt;&gt;&gt; df
   0      1
0  I    30n
1  J     0n
2  J     0n
3  U  1000n
4  C     0n
5  I    12n
6  I    10n
7  I    10n
8  I    10n
9  I    10n


Then you can use the pivot() function:

&gt;&gt;&gt; df.pivot(columns=0)
\     1                 
0    C    I    J      U
0  NaN  30n  NaN    NaN
1  NaN  NaN   0n    NaN
2  NaN  NaN   0n    NaN
3  NaN  NaN  NaN  1000n
4   0n  NaN  NaN    NaN
5  NaN  12n  NaN    NaN
6  NaN  10n  NaN    NaN
7  NaN  10n  NaN    NaN
8  NaN  10n  NaN    NaN
9  NaN  10n  NaN    NaN


If your intention is to write it back to a file you can use to_csv() method.

# this row eliminates the level headers of the columns at level 0
&gt;&gt;&gt; df.columns=df.columns.get_level_values(1)
&gt;&gt;&gt; df
0   C    I   J      U
0      30n           
1           0n       
2           0n       
3               1000n
4  0n                
5      12n           
6      10n           
7      10n           
8      10n           
9      10n           
&gt;&gt;&gt; df.to_csv('new_test_file', index=False)


OR

If you wish to make it less sparse, you can first turn it into a dict and then back to DataFrame:

&gt;&gt;&gt; _dict = df.groupby(0)[1].apply(list).to_dict()
&gt;&gt;&gt; _dict
{'C': ['0n'], 'I': ['30n', '12n', '10n', '10n', '10n', '10n'], 'J': ['0n', '0n'], 'U': ['1000n']}
&gt;&gt;&gt; pd.DataFrame.from_dict(_dict, orient='index')
       0     1     2     3     4     5
C     0n  None  None  None  None  None
I    30n   12n   10n   10n   10n   10n
J     0n    0n  None  None  None  None
U  1000n  None  None  None  None  None

&gt;&gt;&gt; pd.DataFrame.from_dict(_dict, orient='index').T
      C    I     J      U
0    0n  30n    0n  1000n
1  None  12n    0n   None
2  None  10n  None   None
3  None  10n  None   None
4  None  10n  None   None
5  None  10n  None   None


pd.Series.to_dict()
pd.DataFrame.from_dict()
pd.DataFrame.T