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致敬hello world! print("hello world!") print("hello again") print("this is the 3rd line, \n", "and this is also the 3rd line") print("this is the 3rd line, \ and this is also the 3rd line") expression-> number operator _> +-*/ print(4-5) print(8+) 110/12.97 naming number_of_cars = 34 x = 8 if x < 7: print(x) if(x < 7): print("x is smaller than 7") Semantics x = 8 if x < 7: print("x is smaller tahn 7") print("x is bigger than 7") variable names, and objects variable and value speed_of_liuxiang = 110/12.97 distance = 1000 time = distance/speed_of_liuxiang print(time) print(time/60) assign new value, Mutable speed_of_ydj= 110/10 time = distance/speed_of_ydj print(time) time = time -1 print(time) data type interger + - * / % // how big is an int? 0b10 0o10 ox10 float 98.5 type(a) import math math.pi math.e math.floor(98.6) math.ceil(98.6) math.pow(2,3) math.sqrt(25) Boolean 1 < 2 (2< 1) or(1<2) not(2<1) type(a) Strings s = 'this is a string' type(s) print(s) ‘’‘this is the first line this is the second line’‘’ type conversions a = str(98.6) a type(a) float('98.6') int('-123') 1 + 2.0 True + 3 3.88 +"28" combine & duplicate template = "my name is " name = "ydj" greeting = template + '' " + name+" ." print(greeting)
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