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 字典中获取信息并遍历它以进行循环。 将根据单元从字典中获取正确的 email 地址。

当我执行我的代码时，它会在列表的每个成员上循环三遍，我不知道如何让它不这样做。 我相信最初的 for 循环执行得很好并且得到了金属，但是第二个循环使它每个项目运行 3 次，我该如何解决它？

我意识到这很愚蠢，但我一定是在某个地方犯了根本性的错误，在过去 5 个小时试图弄清楚之后，现在是时候寻求帮助了。

# 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 output：

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，更改此：

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')

没有规则说您需要遍历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:
        ...