Dictionaries have several useful built-in methods for altering dictionary values.

• Updating/adding to a dictionary: A dictionary can be updated by passing in an iterable object with key:value pairs (usually another dictionary) into the update method. In the example below, the "apple" key is assigned the new value "green".

dict = {
	"banana": "yellow",
	"apple": "red",
	"grape": "purple"
}
dict.update({"apple": "green"})

Additionally, if a key/value pair that doesn't exist in the dictionary is passed through the update method, it is added. This is shown below.

dict = {
	"banana": "yellow",
	"apple": "red",
	"grape": "purple"
}
dict.update({"tangerine": "orange"})

-Removing values from a dictionary: There are multiple ways of removing values from a dictionary. To remove a specific item, you can use the pop or del method by passing in the key name.

dict = {
	"banana": "yellow",
	"apple": "red",
	"grape": "purple"
}
dict.pop("banana")
del dict["apple"]

If you want to remove the last item in the dictionary, you can use the popitem method.

dict = {
	"banana": "yellow",
	"apple": "red",
	"grape": "purple"
}
dict.popitem() #There are no parameters passed in, since popitem always removes the #last item in the dictionary.

You can also either remove every item from the dictionary using the clear method or delete the structure itself using the del method.

dict = {
	"banana": "yellow",
	"apple": "red",
	"grape": "purple"
}
dict.clear() #dictionary is emptied, but still exists. It can be updated with new items if you want.
del dict #dictionary is actually deleted. Referencing it again will cause an error.

-Looping over a dictionary Like removing items, there are multiple ways of iterating over dictionary items depending on if you want keys, values, or both. You will iterate via a for loop and either use the key method to return only keys, the values method to return only values, or the items method to return the full key:value pair.

dict = {
	"banana": "yellow",
	"apple": "red",
	"grape": "purple"
}
for x in dict.keys():
	print(x)
for x in dict.values():
	print(x)
for x, y in dict.items():
	print(x, y)

Other methods that may be used include:

• copy()
• fromkeys()
• get()
• setdefault()