Python 映射对象是不可下标的

为什么下面的脚本会出现错误:

PayIntList [ i ] = payIntList [ i ] + 1000
TypeError: ‘ map’对象不可下标 

payList = []
numElements = 0


while True:
payValue = raw_input("Enter the pay amount: ")
numElements = numElements + 1
payList.append(payValue)
choice = raw_input("Do you wish to continue(y/n)?")
if choice == 'n' or choice == 'N':
break


payIntList = map(int,payList)


for i in range(numElements):
payIntList[i] = payIntList[i] + 1000
print payIntList[i]
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小开

map() doesn't return a list, it returns a map object.

You need to call list(map) if you want it to be a list again.

Even better,

from itertools import imap
payIntList = list(imap(int, payList))

Won't take up a bunch of memory creating an intermediate object, it will just pass the ints out as it creates them.

Also, you can do if choice.lower() == 'n': so you don't have to do it twice.

Python supports +=: you can do payIntList[i] += 1000 and numElements += 1 if you want.

If you really want to be tricky:

from itertools import count
for numElements in count(1):
payList.append(raw_input("Enter the pay amount: "))
if raw_input("Do you wish to continue(y/n)?").lower() == 'n':
break

and / or

for payInt in payIntList:
payInt += 1000
print payInt

Also, four spaces is the standard indent amount in Python.

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最佳答案

In Python 3, map returns an iterable object of type map, and not a subscriptible list, which would allow you to write map[i]. To force a list result, write 

payIntList = list(map(int,payList))

However, in many cases, you can write out your code way nicer by not using indices. For example, with list comprehensions:

payIntList = [pi + 1000 for pi in payList]
for pi in payIntList:
print(pi)
小开

Don't need to use range for this problem in pypy3 or python3, so it is actually less code..

for i in payIntList: print ( i + 1000 )

and coincidentally matches RustyTom's comment in PhiHag's solution above. Note : Can not reference a map using array brackets [] in pypy3 or python3 or it will throw the same error.

payIntList[i]

Map ref caused the error.


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