Difference between “favor de” and “por favor”

Question

What's the difference between "favor de" and "por favor"?.

Examples:

Favor de lavarse las manos después de ir al baño.

Por favor lávese las manos después de ir al baño.

Hazme favor de sacar la basura.

Por favor saca la basura.

Answer 1

They are very similar, and in most situations they can be translated by "Please, ..."

"por favor" is equivalent to "please" (as adverb, not verb). Typically at the start or end of the phrase, often separated by a comma.

Por favor, saca la basura = Please, take out the rubbish.

Saca la basura, por favor = Take out the rubbish, please.

"Haz/Hazme el favor de [...]" is rather equivalent in meaning, though gramatically different: it requires the article 'el', and the preposition 'de' which connects with the requirement (an alternative: "Hazme el/un favor: saca la basura"). It can also be a little more aggresive (as "Do me a favour:"), but not necessarily.

"Favor de" is more impersonal, to be used in announcements, signs, etc. It's gramatically similar to the previous one, as it implies an ellicited verb "[Haz/Haced/Hagan] el favor de [...]", see above - but the omition suggests that we are not asking anyone in particular.

Answer 2

Hazme favor de sacar la basura.

Do me a favor and take out the rubbish (please)

Por favor saca la basura.

Please take out the rubbish

As for your other two examples, they are pretty much equivalent. I would translate them both as:

Please wash your hands after going to the bathroom

However, the first example could be thought of more as:

After going to the bathroom, do the favor of washing your hands

The use of 'favor de' without the verb hacer afterwards is more common in some areas than others. I never hear it in Argentina yet I think it might be more common in Spain (correct me if i'm wrong)