Here is the code to extract all valid email addresses from the given text, converted into a comma-separated list without spaces: ```python import re def extract_valid_emails(text): # Regular expression pattern to match valid email addresses email_pattern = re.compile(r"[^@\s]+@[^@\s]+\.[^@\s]+") # Extract all matches using the regular expression pattern matches = email_pattern.findall(text) # Join the valid email addresses into a comma-separated string valid_emails = ",".join(matches) return valid_emails # Given text text = """ Contact information: 1. John Doe - john.doe@example.com 2. Jane Smith - jane@smith-family.net 3. support@company.co.uk 4. info@subdomain.example.org 5. Invalid email: not.an.email.com 6. Another invalid: @missing-username.com """ # Extract valid email addresses from the text valid_emails = extract_valid_emails(text) print(valid_emails) ``` The regular expression pattern `[^@\s]+@[^@\s]+\.[^@\s]+` is used to match valid email addresses while ignoring any invalid or whitespace characters. Here's how it works: - `[^@\s]+`: Matches one or more characters that are not `@` or whitespace. This matches the local part of the email. - `@`: Matches the `@` symbol. - `[^@\s]+`: Matches one or more characters that are not `@` or whitespace. This matches the domain name. - `\.`: Matches a literal dot (`.`). - `[^@\s]+`: Matches one or more characters that are not `@` or whitespace. This matches the top-level domain (TLD). The `findall()` method returns a list of all non-overlapping matches of the regular expression pattern in the `text` string. Finally, the `join()` method is used to concatenate the valid email addresses with commas. The output of the code will be: ``` john.doe@example.com,jane@smith-family.net,support@company.co.uk,info@subdomain.example.org ``` This output contains all the valid email addresses from the given text, separated by commas without any spaces.