Python列表理解流控制

问题描述

任何人都可以帮助我获得在函数内部运行的列表理解吗，它是从REPL运行的。 我在while循环的内部和外部尝试了各种缩进和放置，代码将无错误运行，但是未定义/创建了“ newlist”对象。我正在使用此列表理解来拆分collect_places（）的输入字符串。 我不明白为什么理解力不产生新的清单。

输入字符串

'uk, london'

清单理解

newlist = [str.split(',') for str in placeList]

这是代码

import sys
import re

placeList=[]
visits=[[],[]] # created for later use

def collect_places():

"""this function will collect country city pairs"""

while True:
    placed = input('Enter a country and city separated by a comma: ')

    if placed =="":
        sys.exit()

    p=re.search('.*\,.*', placed)

    try:            
        placeList.append(p.group(0))
    except AttributeError as atr:
        print('Try again')        
    continue

newlist = [str.split(',') for str in placeList]

这是脚本和错误

        collect_places()
        Enter a country and city separated by a comma: uk,london
        Enter a country and city separated by a comma: eh
        Try again
        Enter a country and city separated by a comma:

        newlist
        Traceback (most recent call last):
        File “<pyshell#343>”, line 1, in
        newlist
        NameError: name ‘newlist’ is not defined

此操作已成功由REPL执行

        placeList
        [‘uk,london’]

        newlist = [str.split(’,’) for str in placeList]
        newlist
        [[‘uk’, ‘london’]]