What is the situation like in Paris in late December 2019?

In terms of safety, probably nothing special of note, except:

• Avoid areas where demonstrations take place. There are sadly always a few over-excited individuals who play dumb with the police and the police are a bit quick to react these days.

• There are lots of bikes, scooters and other mobility devices everywhere, including on sidewalks where they're supposedly no longer allowed. Keep your eyes open.

In terms of supplies, I wouldn't worry. Yes, there's a lot of traffic and thus deliveries are more difficult than usual, but it's not like it's a siege either.

Hotels and restaurants are more concerned by the fact that there are less customers as people avoid Paris during the strike than the lack of personnel or supplies, as far as I know.

However, in terms of transportation, it can be quite difficult.

• Metro lines 1 and 14 (fully automated) have run every day since the start of the strike, however they can be very, very, very busy at peak hours.

• Lines 4 and 7 have usually run with reduced service and limited stops during peak hours. Again, can be very, very, very busy.

• There are segments of other lines (the Eastern parts of lines 8 and 9 for instance) which have also worked with reduced service. Ditto.

• All other lines have had varying service, ranging from none at all whatsoever to limited and reduced service.

• Note that last Sunday, there was no Metro service at all except lines 1 and 14.

• Bus and tramways lines are quite irregular. Some run (usually with limited service), others don't. You can see a bus that's filled to the brim and the next one will be nearly empty. You will need quite a bit of patience.

• Traffic is bad for cars and Uber-like services. Taxis enjoy bus lanes which, as there are less busses, can be quite easy to navigate at times, except when crossing another street.

• RER has a situation similar to metro.

So it all depends where you are staying, where you want to go, and whether you're averse to walking. If you have a hotel close to line 1 or 14 (ideally both) and avoid peak hours, you can relatively easily travel to all parts of Paris they serve, including the Champs Elysées, Arc de Triomphe, Grand Palais, Place de la Concorde, the Tuileries, the Louvre, Bastille, the "grands magasins" (department stores) Printemps Haussmann and Galeries Lafayette, Ile de la Cité (Notre Dame, what's left of it), Ile Saint Louis, le Marais... The Quartier Latin isn't too far away either.

Getting to the Eiffel Tower will probably need a bit of a walk, but it's flat (from Franklin D. Roosevelt) or downhill (from Charles de Gaulle-Etoile, which is the best approach, go towards Trocadero along Avenue Kleber).

Getting to Montmartre will need a bit of a walk, and it's uphill (quite steeply). You will want to take a taxi for that.

To get to/from airports and train stations taxis are the best option at the moment, though plan for a lot of margin, it can take time to get one, and in some areas with no bus lanes, they're stuck like the rest.

You can probably forget about the Chateau de Versailles, though.

If you have booked a hotel elsewhere, then see if you can cancel and rebook closer to lines 1 and 14. As they have lots of cancellations, there may be quite a few good deals available.

Note that the strike could stop at any time, or be suspended over the Christmas holidays (though this is more likely to happen for long distance trains than for public transit in Paris).

Note that even though long distance train traffic is limited, there are actually trains running to many places (and still seats available on many of those!), and many cities are not affected by public transport strikes, so you could very well come to France but decide to visit some other city/cities. It's a bit difficult to plan, though, as knowing which trains will be running or not is a bit difficult more than a couple of days in advance.