Python好奇心

Question

我很好奇这个程序是如何读取的。你有foo功能。 ＆＃34;东西＆＃34;是一个全局变量。它设置了＆＃34; Thing＆＃34;等于100到＆＃34;项目＆＃34;现在也等于100.返回＆＃34;项目＆＃34; == 0是我不太确定的。 ＆＃34;项目＆＃34;那么等于0？然后下到flag = False。所以＆＃34;当没有标记时：＆＃34;被叫，它要求用户输入，无论出于何种原因，直到你输入＆＃34; 0＆＃34;国旗变为真和＆＃34;事情＆＃34;现在等于0.如果有人可以解释这是如何工作的，我会很感激

def foo(item):
    global thing
    thing = item
    return item == 0

thing = 100
flag = False
while not flag:
    flag = foo(int(input("Give me what I want here: ")))
print(thing)

Answer 1

item设置为用户在提示Give me what I want here时响应的任何内容，转换为整数。反过来，thing也会设置为该值（thing = item将全局thing绑定到item个点。

因此，如果用户输入0，item设置为0，则thing设置为0，item == 0返回{ {1}}，结束True循环。

Answer 2

def foo(item): # 3: item is the int(user_input)
    global thing # 4 :means you are modifying the global variabl 'thing'
    thing = item # 5: you set the global variable 'thing' to equal the int(user_input)
    return item == 0 # 6: you evaluate the int(user_input) to 0, if int(user_input) == 0 it will return True, 
    # else return false


thing = 100
flag = False
while not flag: # 1: while not flag(False) which is the same as while True, a infinite loop
    flag = foo(int(input("Give me what I want here: "))) # 2: takes user input, turns it into a int and call foo with 
    # that value
    # 7 : flag is set to the  whatever is returned from foo, either True if the user input is 0, or false, if not.
print(thing) # 8 if the loop ends(if the int(user_input) == 0) you will print the thing, which is 0, set on set 5. 

---

查看程序流程的一个好方法是打印程序的每一行，也许是一些变量，如下所示：

print ("#1")
def foo(item):
    global thing
    thing = item
    print ("#4 thing=%r, flag=%r,item=%r" % (thing, flag,item))
    return item == 0

thing = 100

flag = False
print ("#2 thing=%r, flag=%r"%(thing,flag))
while not flag:
    print ("#3 thing=%r, flag=%r" % (thing, flag))
    flag = foo(int(input("Give me what I want here: ")))
    print ("#5 thing=%r, flag=%r" % (thing, flag))
print ("#6 thing=%r, flag=%r" % (thing, flag))
print(thing)

输出：

#1
#2 thing=100, flag=False
#3 thing=100, flag=False
Give me what I want here: 1
#4 thing=1, flag=False,item=1
#5 thing=1, flag=False
#3 thing=1, flag=False
Give me what I want here: 0
#4 thing=0, flag=False,item=0
#5 thing=0, flag=True
#6 thing=0, flag=True
0