When to use ‘except’ and when to use ‘except for’?

We use except for before noun phrases.
Example:
The classroom was empty except for a little boy at the back of the room.

We also often use except (for) after generalizing words like ‘all’ ‘any’ ‘every’ ‘no’ ‘everything’ ‘anybody’ ‘nowhere’ ‘nobody’ ‘whole’.
Example:
He ate everything on his plate except (for) the spinach.
Nobody came except (for) Priya and Charu.
You can take any of these dresses except (for) the pink one.

We use except (for) + pronoun (object pronouns)
Example:
We’re all passed except (for) her.

We use except [without for] before prepositions and conjunctions.
Example:
It’s the same everywhere except in India.
It’s the same everywhere except for in India. [incorrect]
This room has no use except as a store room.

We often use except + verb [do……except+infinitive without to][…+ing]
Example: He does nothing except watch TV all day.
She’s not interested in anything except reading.