如何使用键值对迭代列表

Question

有人能帮我解决这个超级新手蟒蛇的问题吗。我试过搜索好几次。

，这是我所提供的列表：

fruits = [{"key":"Red","value":"Apple"},
 {"key":"Yellow-0","value":"Mango"},
{"key":"Green","value":"Banana"}]

在某些情况下也可能是公正的：

fruits = [{"key":"Yellow-0","value":"Mango"}]

问题陈述

我想迭代这个列表，只在有Yellow-0或Yellow-1等的情况下匹配，直到Yellow-9

我的代码

import re

fruits = [{"key":"Red","value":"Apple"},
 {"key":"Yellow-0","value":"Mango"},
{"key":"Green","value":"Banana"}]

keyword = r"Yellow-\d"

for key in fruits:
    if keyword:
        print(fruits)

我的输出

[{'key': 'Red', 'value': 'Apple'}, {'key': 'Yellow-0', 'value': 'Mango'}, {'key': 'Green', 'value': 'Banana'}]
[{'key': 'Red', 'value': 'Apple'}, {'key': 'Yellow-0', 'value': 'Mango'}, {'key': 'Green', 'value': 'Banana'}]
[{'key': 'Red', 'value': 'Apple'}, {'key': 'Yellow-0', 'value': 'Mango'}, {'key': 'Green', 'value': 'Banana'}]

我想要的输出是匹配黄-0并返回true，因为这将是函数的一部分。

Yellow-0

Answer 1

我还没有在Python中使用正则表达式，但这可能会奏效：

pattern = re.compile("Yellow-\d")
for fruit in fruits:
      if pattern.match(fruit['value']):
          print(fruit['value'])

如果它在钥匙里..。

pattern = re.compile("Yellow-\d")
for fruit in fruits:
      match = fruit['value'] if pattern.match(fruit['value']) else False
      match = fruit['key'] if not match and pattern.match(fruit['key']) else False
      if match:
          print(match)

使用三元运算符，var = [value_1] if [condition] else [value_2]会将事情组织起来，这样就不会有嵌套的if/ you语句来干扰代码。

Answer 2

为什么不使用它就导入re？

你有一份字典列表：

for fruit in fruits:
      for key, value in fruit.items():
            if value ==  <your string>:
                  print(value) 

Answer 3

您没有正确地实现您的列表，这里有一个简单的解决方案，不需要导入某些库。希望能帮上忙

#the name 'key' and 'value' are hundled by the dictionary brakets "{}" for that 
you do not need to write them

fruits = [{ "Apple": "Red"}, {"Mango": "Yellow-0"}, {"Banana": "Green"}]

#this is the string value you search for

DesiredString = "Yellow-0"

#Nested for loop to iterate over two stage [the fruit stage, and the key_value 
stage

for fruit in fruits :
    for key, value in fruit.items() :
        if value == DesiredString :
            print(key)