How often does a snake shed?

The frequency of shedding can be different amongst various species of snakes.  But as a general rule, young snakes shed when they outgrow their old skin (similar to children outgrowing clothes) and this would depend on how much and how often they eat. 

Generally adult pythons shed their skins approx every 2 months, but have been known to not shed for up to 2 years.  It has also been noted that snakes may shed after being injured, possibly to aid in the healing process.