Python: Getters and setters

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In languages such as Java, a common style is to use getters and setters for instance variables using functions get and set.

Here is an example in Python (that ignores any error checking).

Here is the Python code [#1]

class colors():
	def __init__(self):
		self.colorDict1 = {
			"red" : "FF0000",
			"green" : "00FF00",
			"blue" : "0000FF"
			}
	def get(self, color1):
		hex1 = self.colorDict1[color1]
		return hex1
	def set(self, color1, hex1):
		self.colorDict1[color1] = hex1
colors1 = colors()
color1 = "red"
hex1 = colors1.get(color1)
print("{0:s} is {1:s}".format(color1,hex1))
color2 = "yellow"
colors1.set(color2,"FFFF00")
hex2 = colors1.get(color2)
print("{0:s} is {1:s}".format(color2,hex2))

Here is the output of the Python code.

red is FF0000
yellow is FFFF00

Note: In Java, the colorDict1 can be hidden from outside - private or protected. In Python, it can not be easily hidden - private or protected. Here is the Python code [#2]

class colors():
	def __init__(self):
		self.colorDict1 = {
			"red" : "FF0000",
			"green" : "00FF00",
			"blue" : "0000FF"
			}
	def __getitem__(self, color1):
		hex1 = self.colorDict1[color1]
		return hex1
	def __setitem__(self, color1, hex1):
		self.colorDict1[color1] = hex1
colors1 = colors()
color1 = "red"
hex1 = colors1[color1]
print("{0:s} is {1:s}".format(color1,hex1))
color2 = "yellow"
colors1[color2] = "FFFF00"
hex2 = colors1[color2]
print("{0:s} is {1:s}".format(color2,hex2))

Here is the output of the Python code.

red is FF0000
yellow is FFFF00

In summary, the use of __getitem__ and __setitem__ makes for nicer code.

Before: (without)

colors1.set(color2,"FFFF00") hex2 = colors1.get(color2)

After: (with)

colors1[color2] = "FFFF00" hex2 = colors1[color2]

It can now be seen that the getting and setting of dictionary keys and list elements using square brackets is a much more general concept in the Python language.

Note: C# has this feature using square brackets. Java does not.