python - Add constant value column that changes half way down to pandas dataframe -

i have list:

[['abc', 1, 2, 3], ['bfg', 4, 5, 6], ['abc', 7, 8, 9], ['bfg', 10, 11, 12]] 

and make pandas dataframe, returns (after adding column color lst[4] = 'blue'):

     0   1   2   3     4 0  abc   1   2   3  blue 1  bfg   4   5   6  blue 2  abc   7   8   9  blue 3  bfg  10  11  12  blue 

is there anyway make return instead:

     0   1   2   3     4 0  abc   1   2   3  blue 1  bfg   4   5   6  blue 2  abc   7   8   9  red 3  bfg  10  11  12  red 

solution dataframe.from_records:

lst = [['abc', 1, 2, 3], ['bfg', 4, 5, 6], ['abc', 7, 8, 9], ['bfg', 10, 11, 12]] df = pd.dataframe.from_records(lst) print (df)       0   1   2   3 0  abc   1   2   3 1  bfg   4   5   6 2  abc   7   8   9 3  bfg  10  11  12 

add values loc:

l = len(df.index) // 2  df.loc[:l - 1, 4] = 'blue' df.loc[l:, 4] = 'red' print (df)      0   1   2   3     4 0  abc   1   2   3  blue 1  bfg   4   5   6  blue 2  abc   7   8   9   red 3  bfg  10  11  12   red 

more interesting if there odd length of df - floor division //:

lst = [['abc', 1, 2, 3], ['bfg', 4, 5, 6], ['abc', 7, 8, 9],         ['bfg', 10, 11, 12], ['bfg', 3, 4, 5]] df = pd.dataframe.from_records(lst) print (df)      0   1   2   3 0  abc   1   2   3 1  bfg   4   5   6 2  abc   7   8   9 3  bfg  10  11  12 4  bfg   3   4   5  l = len(df.index) // 2  df.loc[:l, 4] = 'blue' df.loc[l:, 4] = 'red' print (df)      0   1   2   3     4 0  abc   1   2   3  blue 1  bfg   4   5   6  blue 2  abc   7   8   9   red 3  bfg  10  11  12   red 4  bfg   3   4   5   red 

or normal division /:

l = len(df.index) / 2  df.loc[:l, 4] = 'blue' df.loc[l:, 4] = 'red' print (df)      0   1   2   3     4 0  abc   1   2   3  blue 1  bfg   4   5   6  blue 2  abc   7   8   9  blue 3  bfg  10  11  12   red 4  bfg   3   4   5   red