df1 = pd.read_csv(io.StringIO('''value1   value2   value3     ID   text
-0.1    0.35    -0.5       4    THIS
-0.2    0.05    -0.7       3    IS
0.1     0.1     0.8        5    DRIVING'''), sep='  {2,}')
__main__:4: ParserWarning: Falling back to the 'python' engine because the 'c' engine does not support regex separators (separators > 1 char and different from '\s+' are interpreted as regex); you can avoid this warning by specifying engine='python'.

df1
Out[96]:
   value1  value2  value3  ID     text
0    -0.1    0.35    -0.5   4     THIS
1    -0.2    0.05    -0.7   3       IS
2     0.1    0.10     0.8   5  DRIVING

df2 = pd.read_csv(io.StringIO('''value1   value2   value3     ID   text
-0.1    0.35    -0.5       4    ME
-0.2    0.05    -0.7       3    NUTS'''), sep='  {2,}')
__main__:3: ParserWarning: Falling back to the 'python' engine because the 'c' engine does not support regex separators (separators > 1 char and different from '\s+' are interpreted as regex); you can avoid this warning by specifying engine='python'.

df2
Out[98]:
   value1  value2  value3  ID  text
0    -0.1    0.35    -0.5   4    ME
1    -0.2    0.05    -0.7   3  NUTS

pd.concat([df1,df2], axis=0, ignore_index=True)
Out[99]:
   value1  value2  value3  ID     text
0    -0.1    0.35    -0.5   4     THIS
1    -0.2    0.05    -0.7   3       IS
2     0.1    0.10     0.8   5  DRIVING
3    -0.1    0.35    -0.5   4       ME
4    -0.2    0.05    -0.7   3     NUTS