在一堆行上使用 lstrip 时，只有以 'r' 开头的那些会受到影响，而 'r' 会被删除

Question

我有一个包含一些电子邮件的文本文件。所有这些都开始如下：

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

From: [e-mail]

我的问题是要获得唯一的电子邮件 ID，所以我尝试-

fhand = open("mbox-short.txt")  

emails=[]

for line in fhand:

    if line.startswith("From:"):

        l=line.lstrip("From:").rstrip()

        emails.append(l) 

unique = []

for email in emails:

    if email not in unique:

        unique.append(email)

        print(email)

print("\nTotal Unique Contacts=",len(unique))

输出-

[e-mail]

[e-mail]

[e-mail]

[e-mail]

[e-mail]

[e-mail]

[e-mail]

[e-mail]

[e-mail]

[e-mail]

[e-mail]

唯一联系人总数= 11

这是正确的答案但是-

当我在 lstrip("From: ") 中使用了一个额外的空间时，因为实际的电子邮件在 "From:" 之后开始，这就是我得到的-

fhand = open("mbox-short.txt")  

emails=[]

for line in fhand:

    if line.startswith("From:"):

        l=line.lstrip("From: ").rstrip()

        emails.append(l) 

unique = []

for email in emails:

    if email not in unique:

        unique.append(email)

        print(email)

print("\nTotal Unique Contacts=",len(unique))

输出-

[e-mail]

[e-mail]

[e-mail]

[e-mail]

[e-mail]

[e-mail]   

[e-mail]

[e-mail]

[e-mail]

[e-mail]

[e-mail]

唯一联系人总数= 11

所以我们看到从 r 开始的电子邮件受到影响，因为它们的第一个字母从输出中消失，而其他的则根本不受影响。请帮助我理解为什么会这样。谢谢

Answer 1

让我们从查看以下文档开始lstrip：海峡 lstrip([字符])返回删除了前导字符的字符串的副本。chars 参数是一个字符串，指定要删除的字符集。这意味着您的代码的以下部分：line.lstrip("From: ")从左边开始删除所有出现的F, r, o,和空格m，:直到找到另一个字符。一些例子：>>> "From: [e-mail]".lstrip("From: ")'[e-mail]'>>> "From: [e-mail]".lstrip("From: ")'@example.com'>>> "  mmmrrroooFFF: [e-mail]".lstrip("From: ")'[e-mail]'

Answer 2

使用str.split()amd 然后访问第一个元素。您还可以使用 aset来获取所有唯一的电子邮件。前任：emails = set()with open("mbox-short.txt") as fhand:    for line in fhand:        if line.startswith("From:"):            emails.add(line.strip().split()[1])print(emails)print("\nTotal Unique Contacts=",len(emails))

Answer 3

您也许可以re用来获取这些邮件：import rewith open("mbox-short.txt", 'r') as f:    emails= list(set(re.findall(r'[\w\.]+@[\w\.]+', f.read())))