TypeError: '>=' not supported between instances of 'tuple' and 'float'

Question

I am trying to write a little python script that calculates the Tanimoto similarity index between a molecule of interest and a database of molecules. I am using pybel.

The database, in the .smi format, have chemical information of molecules on the first column and their names as a second one and looks like this:

C[C@]12CC[C@H](C1(C)C)CC2=O     (-)-CAMPHOR
CC1=CC[C@H](C(=C)C)C[C@@H]1O    (-)-CARVEOL
CC1=CC[C@H](CC1=O)C(=C)C        (-)-CARVONE
O=CC[C@@H](C)CCC=C(C)C  (-)-CITRONELLAL
OCC[C@@H](C)CCC=C(C)C   (-)-CITRONELLOL
C[C@@H]1CC[C@@H](C(=C)C)C[C@H]1O        (-)-DIHYDROCARVEOL
C[C@@]12CC[C@@H](C1)C(C2=O)(C)C (-)-Fenchone
C[C@@H]1CC[C@H]([C@@H](C1)O)C(C)C       (-)-MENTHOL
C[C@@H]1CC[C@H](C(=O)C1)C(C)C   (-)-MENTHONE
C[C@@H]1CCCCCCCCCCCCC(=O)C1     (-)-MUSCONE
CC(=C)[C@H]1CCC(=CC1)C=O        (-)-PERILLALDEHYDE
.
.
.

This version of the script works as I expect:

from openbabel import pybel

targetmol = next(pybel.readfile("smi", "/path/to/sample.smi"))

targetfp = targetmol.calcfp()              <--- calculate fingerprints of the sample

for mol in pybel.readfile("smi", "/path/to/db.smi"):

    fp = mol.calcfp()                      <--- calculate fingerprints of the db

    tan = fp | targetfp                    <--- calculate the Tanimoto index via the "|" operator

    if tan>=0.8:

        print(tan)

Output:

1.0
1.0
0.9285714285714286
0.8571428571428571
1.0
1.0
0.9285714285714286
0.8571428571428571
.
.
.

Clearly, in order to give a meaning to the numbers I receive, I need to add the molecule name to the corresponding Tanimoto index. I tried this:

from openbabel import pybel

targetmol = next(pybel.readfile("smi", "/path/to/sample.smi"))

targetfp = targetmol.calcfp()              

for mol in pybel.readfile("smi", "/path/to/db.smi"):

    fp = mol.calcfp()                      

    tan = (fp | targetfp, mol.title)                   

    if tan>=0.8:

        print(tan, title)

As from the title, I receive the following error:

Traceback (most recent call last):
  File "test3.py", line 15, in <module>
    if tan>=0.8:
TypeError: '>=' not supported between instances of 'tuple' and 'float'

My guess is that python, obviously, cannot apply the if tan>=0.8 operation to a string format but I really do not know how to overcome this problem since, as you can guess, I am very new to programming.

Any hints on how to correct this piece of code will be appreciated. Thank you for your time.

Answer 1

You just have to change it to: tan[0] >= 0.8:

the comma , (the one inside tan = (fp | targetfp, mol.title)) is the syntax for a tuple, which is basically a not mutable array, so to access elements you need to do it by index like for lists.