grammar of python
input:
default input is string
num=input()
num=int(input())//this can change the input type
loop:
instead of curly brackets, python identify code block by retract（indented)
for i int range(1,10,2):
//range is [1,10) which means [1,9]
for i in [2,5,"cheese",' ']:
print(i*2)
//the output is:
4
10
cheesecheese
division
/is not rounded
\\ is rounded
if else :
if x and y:
print(1)
elif x:
print(0)
else:
print(-1)