Perhaps rather than Catalan political parties it would be more accurate to say political parties in Catalonia because some are specific to Catalonia, some are more Spanish and some are a mixture.
The political make-up in Catalonia is complex to say the least because parties are not only divided along traditional left-right lines but there are also differences based on nationalist politics.
Some parties favour complete independence of Catalonia from Spain, others want to negotiate a new relationship with the central Spanish government including possibly a federal solution whilst a third group of parties favours the maintenance of the status quo or even a reduction in Catalonia's autonomous powers.
The accompanying graphic from 2015 is a little out of date but gives a rough idea of many of the Catalan parties on both issues with left-right on the horizontal axis and Catalanism-Spanish nationalism on the vertical axis.
Based on the election results of December 21st 2017, there are currently
seven different political parties or coalitions represented in the
Parliament of Catalonia and the 135 seats are distributed as follows.
The pro-independence coalition Junts pel Sí, which had 62 seats in the last Parliament broke down into its component parts of PDECat, under the name of Junts per Catalunya, and Esquerra Republicana for the December 21st 2017 election, won a total of 66 seats (34 and 32 respectively). This is a further development of the relationship between the two major pro-independence parties since the Catalan independence movement really to centre stage in Catalan politics after the Catalan National Day or Diada of September 11th 2012.
At the time the ruling party was the coalition Convergència i Unió led by Artur Mas, which had dominated the Parliament of Catalonia since Spain's Transition to Democracy after the death of General Franco in 1975. Convergència's commitment to Catalan independence led to the break up of CiU and a financial scandal involving its legendary founder, Jordi Pujol, has led the party to change its name to Partit Demòcrata Europeu de Catalunya (PDECat). It is currently suffering from something of an identity crisis and as you can see from the poll below is losing a lot of support.
In 2012, Esquerra Republicana was very much the junior partner in the Catalan independence movement but due to the perception that it is the party that is most committed to achieving independence for Catalonia, it's popularity has steadily increased and if elections to the Parliament of Catalonia were held today, Esquerra would be easily the most voted party.
The far left Candidatura d'Unitat Popular or CUP is another pro-independence party, which was virtually unheard of prior to 2012 but has had a massive influence on the last legislature. This influence made them unpopular with many voters and they have dropped from 10 seats to 4.
Catalunya En Comú is an umbrella party including left-wing parties such as Iniciativa per Catalunya and the Spanish party, Podemos. They aren't in favour of independence but do support a referendum. In future elections, they would probably go under the name of Catalunya Sí Que Es Pot.
The rest of the parties are all against independence for Catalonia. Ciutadans are now the largest party in the Parliament of Catalonia and were founded in Catalonia but fielded many candidates in the Spanish elections.
PSC are the Catalan affiliate of the Spanish socialists, PSOE, and the Partido Popular are part of the ruling Spanish conservatives. There has been a redistribution and slight in support for the anti-independence parties in general.