#这是注释
print("Hello World")

#当语句以冒号:结尾时，缩进的语句视为代码块
a = 100
if a >= 0:
    print(a)
else:
    print(-a)

print(10/3)
print(10//3)

print('I\'m learning\nPython.')

print(r'\\\t\\')

print('''窗前明月光，
疑是地上霜。
举头望明月，
低头思故乡。''')

print(r'''hello,\n
world''')

True
False

print('3>2: ', 3 > 2)
print(None)

a = 123 # a是整数
print(a)
a = 'ABC' # a变为字符串
print(a)

a = 'ABC'
b = a
a = 'XYZ'
print(b)