计算2 3 4 加运算符 小于30

>>> new=[''.join(('2',op,'3')) for op in ops]

>>> print(new)

['2+3', '2-3', '2*3', '2/3', '23']

>>> new=[''.join(('2',op,'3',op,'4')) for op in ops]

>>> print(new)

['2+3+4', '2-3-4', '2*3*4', '2/3/4', '234']

>>> new=[]

>>> for op1 in ops:

		for op2 in ops:

			new1=''.join(('2',op1,'3',op2,'4'))

			new.append(new1)

		print(new)

	len(new)

['234', '23+4', '23-4', '23*4', '23/4']

5

['234', '23+4', '23-4', '23*4', '23/4', '2+34', '2+3+4', '2+3-4', '2+3*4', '2+3/4']

10

['234', '23+4', '23-4', '23*4', '23/4', '2+34', '2+3+4', '2+3-4', '2+3*4', '2+3/4', '2-34', '2-3+4', '2-3-4', '2-3*4', '2-3/4']

15

['234', '23+4', '23-4', '23*4', '23/4', '2+34', '2+3+4', '2+3-4', '2+3*4', '2+3/4', '2-34', '2-3+4', '2-3-4', '2-3*4', '2-3/4', '2*34', '2*3+4', '2*3-4', '2*3*4', '2*3/4']

20

['234', '23+4', '23-4', '23*4', '23/4', '2+34', '2+3+4', '2+3-4', '2+3*4', '2+3/4', '2-34', '2-3+4', '2-3-4', '2-3*4', '2-3/4', '2*34', '2*3+4', '2*3-4', '2*3*4', '2*3/4', '2/34', '2/3+4', '2/3-4', '2/3*4', '2/3/4']

>>> new=[]

>>> for op1 in ops:

		for op2 in ops:

			new1=''.join(('2',op1,'3',op2,'4'))

			if eval(new1)<30:

				new.append(new1)

>>> print(new)

['23+4', '23-4', '23/4', '2+3+4', '2+3-4', '2+3*4', '2+3/4', '2-34', '2-3+4', '2-3-4', '2-3*4', '2-3/4', '2*3+4', '2*3-4', '2*3*4', '2*3/4', '2/34', '2/3+4', '2/3-4', '2/3*4', '2/3/4']