Safe to walk at night?

The Pigalle - Montmartre neighborhoods are bustling with tourists with a significant nightlife, there is no reason to worry.

If by 'at night' you meant to suggest it might be unsafe, bear in mind that after dinner (around 10 PM) is a very standard time to be walking the streets of Paris.

Just be careful not to get run over by one of the many tourist buses while crossing the street. :-)

You might want to look on Google Maps Street view and check out the shops on the blocks you will travel. There is a stretch that isn't exactly PG, ( it is the red light district after all), but you would be physically safe.

We have friends who live near the Barbes stop and we in the fall rent a place in Batignolles which is maybe a mile or a mile and a half walk away -- we often walk this at 11 pm or 12. Montmartre is tourist central and bustling with people on the street till late and we have never felt nervous walking there or the longer stretch to where we stay. Paris is an extremely safe town for violence. Pickpockets are ubiquitous in crowded spaces like the metro or the Eiffel Tower or Louvre -- but that is not a safety issue and it is easy to not be a victim by not carrying valuables in easily picked places (including front pockets)

My general experience walking in Paris is that the early morning hours (5-6 am) are probably far more of an issue than the late hours of the evening. At 5-6 am you can encounter those who were partying all night and may or may not be on their way home, but almost always under the influence. Fortunately I was walking with my adult son, but we encountered several people worse for wear, observed a few loud altercations, and were asked if we wanted to buy cocaine.......

Evenings were never an issue.

Edit to add: No, we weren't out partying. We were walking a distance to the one bakery that was open that early in the morning for breakfast.