如何在嵌套的 for 循环中遍历列表和字典

Question

我正在使用 python 3.9 并尝试从 python 列表和 python 字典中获取信息并循环遍历它。将根据单位从字典中提取正确的电子邮件地址。

当我执行我的代码时，它在列表的每个成员上循环三次，我不知道如何让它不那样做。我相信初始的 for 循环执行正常并获得了金属，但这是第二个循环使每个项目运行三次，我该如何修复它？

我意识到这很不靠谱，但我一定是在某个地方犯了根本性错误，在过去 5 个小时试图解决这个问题之后，现在是寻求帮助的时候了。

# Dictionary of metals and email addresses
metals = {
    'gold':'1@gmail.com',
    'silver':'2@gmail.com',
    'platinum':'3@gmail.com',
}

# Variable holding some string data
gold = """
Gold is a chemical element with the symbol Au and atomic number 79, 
"""
silver = """
Silver is a chemical element with the symbol Ag and atomic number 47. 
"""
platinum = """
Platinum is a chemical element with the symbol Pt and atomic number 78.
"""

units = [gold, silver, platinum]

# What I want to do is have a loop where it takes the item in the list
#, for example, gold, matches it with the key to that in the dictionary, thereby
# enabling me to send gold to 1@gmail.com, silver to 2@gmail.com, and platinum to
# 3gmail.com

for unit in units:
    for metal in metals.items():
        if unit == gold:
            email_address = metals.get('gold')
            print(email_address)
        elif unit == silver:
            email_address = metals.get('silver')
            print(email_address)
        elif unit == platinum:
            email_address = metals.get('platinum')
            print(email_address)
        else:
            print('No Match')

# just some code to print out various bits of information
# Print our Dictionary Keys
for k in metals.keys():
    print('Keys: ' + k)

# Print our dictionary Values
for v in metals.values():
    print('Values: ' + v)

# print out the values held in our list
for item in units:
    print('Items: ' + item)

这是输出：

1@gmail.com
1@gmail.com
1@gmail.com
2@gmail.com
2@gmail.com
2@gmail.com
3@gmail.com
3@gmail.com
3@gmail.com
Keys: gold
Keys: silver
Keys: platinum
Values: 1@gmail.com
Values: 2@gmail.com
Values: 3@gmail.com
Items: 
Gold is a chemical element with the symbol Au and atomic number 79, 

Items: 
Silver is a chemical element with the symbol Ag and atomic number 47. 

Items: 
Platinum is a chemical element with the symbol Pt and atomic number 78.

Answer 1

只需删除内部 for 循环，更改为：

for unit in units:
    for metal in metals.items():
        if unit == gold:
            email_address = metals.get('gold')
            print(email_address)
        elif unit == silver:
            email_address = metals.get('silver')
            print(email_address)
        elif unit == platinum:
            email_address = metals.get('platinum')
            print(email_address)
        else:
            print('No Match')

对此：

for unit in units:
    if unit == gold:
        email_address = metals.get('gold')
        print(email_address)
    elif unit == silver:
        email_address = metals.get('silver')
        print(email_address)
    elif unit == platinum:
        email_address = metals.get('platinum')
        print(email_address)
    else:
        print('No Match')

没有规则规定您需要迭代 metals 才能调用 metals.get。

Answer 2

metals.items()中有 3 个项目。这就是循环运行 3 次的原因。只需删除该声明；你不需要那个循环

for unit in units:
    if unit == gold:
        ...

如何在嵌套的 for 循环中遍历列表和字典

How to iterate through a list and a dictionary in a nested for loop

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