python2与python3区别（一）

Python2中这样写：

print "welcome to china!"

python3中要这样写：

print ("welcome to china!")

实现加减乘除：

python2中这样写：

#from pip._vendor.distlib.compat import raw_input
a = input("please input first number:")
b = input("please input second number:")
print("a+b=",a+b)
print("a-b=",a-b)
print("a*b=",a*b)
print("a/b=",a/b)

python3中这样写：

from pip._vendor.distlib.compat import raw_input

a = int(raw_input("please input first number:"))
b = int(raw_input("please input second number:"))
print("a+b=",a+b)
print("a-b=",a-b)
print("a*b=",a*b)

print("a/b=",a/b)

若不加from pip._vendor.distlib.compat import raw_input，则

会出现错误：

TypeError: unsupported operand type(s) for -: 'str' and 'str'