str repr and format

相比js 或者 c#中的toString(), python 的 3个magic method更加灵活

class Point2D:
	def __init__(self, x, y):
		self.x = x
		self.y = y

	def __str__(self):
		return '({},{})'.format(self.x, self.y)

	def __repr__(self):
		return 'Point2D(x={}, y={})'.format(self.x, self.y)

	def __format__(self, f):
		if f =='r':
			return '{}, {}'.format(self.y, self.x)
		else:
			return '{}, {}'.format(self.x, self.y)

__str__ is used to display infomation to the users

__repr__ is used to display infomation to developer

__format__ will be used in .format function

when you want to show a large list of object using repr method, it will be hard to read, then we can use reprlib.repr method, it will show partial list of the entire list

ascii ord chr

ascii replaces non-ASCII characters with escape sequences

ord converts a single character to its interger unicode codepoint

chr converts an integer unicode codepoint to a single character string