整型或浮点型转str字符串类型
s1=3.14
print(type(s1))
s2=int(s1)
print(s2)
s3=str(s2)
print(s3,type(s3))
返回值：
<class 'float'>
3
3 <class 'str'>
布尔值转换：
s1=1
s2=0
s3=0.0
s4="0"
s5=""
print(bool(s1),type(s1),"\n")
print(bool(s2),type(s2),"\n")
print(bool(s3),type(s3),"\n")
print(bool(s4),type(s4),"\n")
print(bool(s5),type(s5),"\n")
返回值：
True <class 'int'>
False <class 'int'>
False <class 'float'>
True <class 'str'>
False <class 'str'>