"L'office du tourisme" can also be written as "l'office de tourisme". The noun is le tourisme (masculine). Either version (with or without "le", i.e., de as well as du) are correct and in use.

L'office de/du tourisme. -- The tourist office, office of tourism
Le guide de la ville. -- The city guide, a guide of the city
Je viens du super marché -- I'm coming from the supermarket.

The topic when to use "de" and when "de la", "du" or "des" can be a bit tricky. Even though your question links to the lesson for the partitive article, none of your examples contain a partitive article. Just making sure you're aware of it.

Hi Fawad,

The key aspect of grammar that you will need to master is Articles.

In English we use "the" but in French le, la, or l' with single nouns and les before plural nouns.

Le and les compound with à and de to produce au, aux and du, des (of the).

So I suggest you revisit definite, indefinite, and partitive articles to aid your further understanding.

Hope this helps.

Jim

so basically the way i learned it was that for feminine nouns, when you use the partitive article, you say "de la" but for masculine nouns it is "du" and then there's also "de l'" for nouns that start with a vowel/h muet, and then des for plural nouns.  they all mean the same it depends on the noun. so basically you'd say "some food" = "de la nourriture" & "some milk" = "du lait". de la and du are the same. to answer your other question, de + les = des, and de+le = du, de la stays the same and doesn't combine. 

SO, it would be où se trouve l'office  du tourisme?  because tourisme is a masculine noun; le tourisme: the tourism. du can be used as "of the" because de+le means of + the and combines to make du.  for "avez-vous un guide de la ville?" it is just de la because "ville" is feminine and they dont combine. for "je viens du super marche," du can mean from + the. 

in contracted articles  All these forms of 'de' whoch are - du, de la , de l' and des . They all mean "of the" or "from the".

So the meaning of hour example - je viens DU super marché . Is ( i came back from the super market)

in contracted articles  All these forms of 'de' whoch are - du, de la , de l' and des . They all mean "of the" or "from the".

So the meaning of hour example - je viens DU super marché . Is ( i came back from the super market)

or you can say that - i Am coming from the super market .

In contracted articles 'de' forms mean- "of the , from the". And 'a ' forms mean " to the , at the".

Merci ! 

or you can say that - i Am coming from the super market .

In contracted articles 'de' forms mean- "of the , from the". And 'a ' forms mean " to the , at the".

Merci !