Farms with comments

import sys

# classes definitions
class CollectiveFarm:
    def __init__(self, name):
        self.name = name
        self.species = []

class Specie:
    def __init__(self, name):
        self.name = name

# creating species
Species = {
    'Rye' : Specie('Rye'),
    'Teff' : Specie('Teff'),
    'Oat' : Specie('Oat'),
    'Rice' : Specie('Rice')
    }

# creating farms
Minsk = CollectiveFarm('Minsk')
Yobastan = CollectiveFarm('Yobastan')
Yoptastan = CollectiveFarm('Yoptastan')

# adding species to farms
Minsk.species = [ Species['Rye'], Species['Teff'], Species['Oat'] ]
Yobastan.species = [ Species['Rye'], Species['Teff'], Species['Rice'] ]
Yoptastan.species = [ Species['Rye'], Species['Teff'] ]

# adding farms
Farms = [Minsk, Yobastan, Yoptastan]

# main program
def main():
    common_species = Farms[0].species # using first farm as init value
    print('Farms: ')
    for farm in Farms:
        # printing all farms for user
        print(farm.name)
        # replacing common_species with a intersetion of farm.species
        # this is logically equal to comparing set(common_species) & set(farm.species), which gives uniqes
        # each loop we'll throw out species that not being common to either previous filtering or current one
        common_species = set(common_species).intersection(farm.species)

    # printig all species for user
    print('\n')
    print('Species:')
    for name, specie in Species.items():
        print(specie.name)

    # printing FILTERED common species
    # should only contain species that's been found in all farms
    print('\n')
    print('Common species:')
    for specie in common_species:
        print(specie.name)

    # part2, display species for specific farm
    print('\n')
    # getting user input
    farmid = input('Enter farm name or farm index to display species: ')

    try:
        # we expect user typed integer, try to convert it to int index
        farmid = int(farmid)
        farm = Farms[farmid]
    except ValueError:
        # otherwise try to directly select farm from list
        try:
            farm = [_ for _ in Farms if _.name == farmid][0]
        except IndexError:
            print('%s not found in farms' % farmid)
            sys.exit()

    # displaying selcted farm species
    print('%s farm species' % farm.name)
    for specie in farm.species:
        print(specie.name)

if __name__ == '__main__':
    main()