我正在使用python 3.3.2并且我正在编写一个带有数字的程序，并按升序将其添加到列表中。该程序有效，但我添加了一个语句，检查用户输入的数字是否已经在列表中，当它为真时，循环结束并且程序停止。有人可以给我任何建议，为什么会这样，以及如何预防？
L = float(input('Input a number: ')) #Gets input from user
list1 = [L] #Places the first input in a list
for L in list1: #Begins loop
L = input('Input a number: ') #More input
if L == ('stop'): #User tells program to stop
print(list1)
break #Ends program
elif L != ('stop'): #The user does not stop the program
L = float(L)
if L not in list1: #New input not in list
N = len(list1)#Length of list
M = max(list1)#Max value of list
m = min(list1)#Min value of list
if L < m: #Checks if input is smaller than the min of list1
list1.insert(0, L)#Inserts new input at start of list
elif L > M:#Chacks if new input is larger than the max of list1
list1.append(L)#Add new input at ent of list1
elif L < M and L > m:#New input is between max and min of list1
for x in range(0 , len(list1)):#x is the number of indexes in list1
if L < list1[x]:#Checks the size of each index to the input
list1.insert(x, L)#Inserts input between upper and lower values
break
elif L in list1: #Checks if new input is already in list
print ('Already in list!')
else: #Program fails
print('I\'m afraid I can\'t do that Dave.')#LOL
break
感谢。