"""A collection of update operations for TinyDB.They are used for updates like this:>>> db.update(delete('foo'), where('foo') == 2)This would delete the ``foo`` field from all documents where ``foo`` equals 2."""
[docs]defdelete(field):"""    Delete a given field from the document.    """deftransform(doc):deldoc[field]returntransform
[docs]defadd(field,n):"""    Add ``n`` to a given field in the document.    """deftransform(doc):doc[field]+=nreturntransform
[docs]defsubtract(field,n):"""    Subtract ``n`` to a given field in the document.    """deftransform(doc):doc[field]-=nreturntransform
[docs]defset(field,val):"""    Set a given field to ``val``.    """deftransform(doc):doc[field]=valreturntransform
[docs]defincrement(field):"""    Increment a given field in the document by 1.    """deftransform(doc):doc[field]+=1returntransform
[docs]defdecrement(field):"""    Decrement a given field in the document by 1.    """deftransform(doc):doc[field]-=1returntransform