Python Note 2

Python中每一个数据类型实际上都是一个类。

Function definition
As python recommended, left two blank lines after function

def greet_user():
    print("GO")
    print("Hi THERE!")


greet_user()

Function parameters

def greet_user(name):
    print(f"GO:{name}")
    print("Hi THERE!")


greet_user("John")
greet_user() #Error, no parameter

def greet_user2(first_name,second_name):
    print(f"GO:{first_name} {second_name}")
    print("Hi THERE!")


greet_user2("John","Smith")
greet_user2(second_name="John",first_name="Smith") #使用keyword形式作为参数，
greet_user2(second_name="John","Smith") #错误，混合情况必须先用position形式再用keyword形式

Funtion Returns
By default, python return none.

def square(number):
	return number * number


result = square(3)
print(result)

Error Handling
try except

try:
	day = int(input("input day:"))
	income = 2000 / day
	print(day)
except ZeroDivisionError:
	print("day can't be zero")
except ValueError:
	print("Invalid input")