Python字符串，整型，浮点数相互转化

str_a = "123"
int_a = int(str_a)
print("num2+1: %d"%(int_a + 1))
# num2+1: 124

str_b = "123.12"
double_a = float(str_b)
print("num2: %f"%(double_a + 1.0))
# num2: 124.120000

num = 123
str_num = str(num)
print("hello %s"%str_num)
# hello 123