Se lo

[Tyrn]

Hi,

Maybe a silly question, yet I can't answer it myself with any certainty. Does se before lo, la always mean le? Is it really that simple?

[Rusty]

No, it's not that simple.

There are times when 'se' is a reflexive (pronominal) pronoun. There are also passive constructs, and impersonal or accidental usages, to consider.

If those usages can be ruled out, that leaves the possibility of seeing 'se' followed by another pronoun. If both pronouns are third-person pronouns, then you have the condition you may have asked about in the first place.

User wrholt once posted the following.
If there are two or three object pronouns accompanying the verb, the relative order of the pronouns is fixed:

1. 'se' (third person reflexive/pronominal object, or substitute for third-person indirect object = le or les when a third-person direct object is necessary)

2. 'te' or 'os' (second person direct, indirect, or reflexive/promominal object)

3. 'me' or 'nos' (first person direct, indirect, or reflexive/pronominal object)

4. 'le', 'les', 'lo', 'la', 'los' or 'las' (third-person indirect object [only le or les], and third-person direct object [only lo, la, los or las])

Any one pronoun may appear only once in each pronoun group. For each position, at most 1 pronoun from the choices for that position may appear.

You can go to the authority on the matter here (https://www.rae.es/dpd/pronombres+personales+%2525C3%2525A1tonos) (la acepción 4, en particular).

Since your question deals with only the third-person pronouns, we can count on seeing 'se' listed first (rule number 1). It replaces the indirect object pronoun. The remaining direct object pronoun is covered by rule number 4.