数组作为位置参数

Question

try:
    target = int(input("Please enter the ammount you are looking for :"))
except ValueError:
    print("wrong value please enter a number")
    target = int(input("Please enter the ammount you are looking for :"))
found = False
location = [] # I want to use this list as position argument for another array passed from another function. is it possible?


for pos in range(0, len(wydatki)):
    if wydatki[pos] == target:
        found=True
        location.append(pos)

if found==True:
    #prints the locations in the list that the target was found
    print (target,"\nappears in the following locations: ",months[location])
else:
    print (target,"\nwas not found in the list.")

months[location]

通常你只能使用单个变量来指向数组中的位置？

Answer 1

正如您所注意到的，您不能传递一个列表并将其用作索引。

您必须遍历每个索引，或者构建一个完整的字符串并打印出来。

例如

print(target,"\nappears in the following locations: ", end="")
for index in location:
    print(months[index], end=" ")
print("")

end="" 表示 print 将在末尾添加一个空字符串，而不是通常的新行。

此外，您还可以通过其他两种方式改进您的代码。

布尔值found 可以对应于列表location，其中包含任何值，所以

if location: # an empty list evaluates to False
  print("Found")
else:
  print("Not found")

您的输入可能看起来像这样

target = None
done = False
while not done:
  try:
    target = int( input("Please enter the amount you are looking for:") )
    done = True
  except ValueError:
    print("Wrong value, input a number.")

因此用户可以多次失败，程序将无法继续。

Answer 2

如果你稍微改变一下你的输出，你可以：

target = 42
location = []
# 42 occures at positions 3,6,8
#           0 1 2 3  4 5 6  7 8  9
wydatki = [ 1,2,3,42,4,5,42,6,42,8]

#         pos: 01234567890
months = list("abcdefghijk")

# get the positions unsing enumerate
for pos,value in enumerate(wydatki):
    if value == target:
        location.append(pos)

if location: # empty lists are False, lists with elements are True
    #prints the locations in the list that the target was found
    print (target,"\nappears in the following locations: ", 
           ','.join( (months[a] for a in location) ) )
else:
    print (target,"\nwas not found in the list.")

输出：

42 
appears in the following locations:  d,g,i

基本上，您需要将所有月份条目插入并加入一个字符串 - f.e.在","join( ... ) 语句中使用生成器表达式。