Validate Email Address¶
Check if a string is a valid email address using the standard library.
9 snippets available in this sub-category.
Simple¶
Basic email validation¶
string email validation regex text
Basic email validation using regex pattern
import re
def is_email(text):
"""Basic email validation using regex."""
pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
return bool(re.match(pattern, text))
email = "user@example.com"
result = is_email(email)
print(result) # True
Notes
- Uses regex pattern matching
- Checks basic email format
- Returns boolean
- Simple validation
Email validation with length check¶
string email validation length regex text
Email validation with maximum length check
import re
def is_email_with_length(text, max_length=254):
"""Email validation with length check."""
if len(text) > max_length:
return False
pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
return bool(re.match(pattern, text))
email = "user@example.com"
result = is_email_with_length(email)
print(result) # True
Notes
- Includes length validation
- RFC 5321 compliant length
- Prevents overly long emails
- More robust validation
Complex¶
Comprehensive email validation¶
string email validation comprehensive regex text
Comprehensive email validation with multiple checks
import re
def is_valid_email(text):
"""Comprehensive email validation."""
if not text or len(text) > 254:
return False
# Basic pattern
pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
if not re.match(pattern, text):
return False
# Check for consecutive dots
if ".." in text:
return False
# Check for dots at start/end of local part
local_part = text.split("@")[0]
if local_part.startswith(".") or local_part.endswith("."):
return False
return True
email = "user.name@example.com"
result = is_valid_email(email)
print(result) # True
email2 = "user..name@example.com"
result2 = is_valid_email(email2)
print(result2) # False
Notes
- Multiple validation rules
- Checks for common issues
- RFC compliant
- Robust validation
Email validation with domain check¶
string email validation domain regex text
Email validation with domain format checking
import re
def is_email_with_domain_check(text):
"""Email validation with domain existence check."""
# Basic email validation
pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
if not re.match(pattern, text):
return False
# Extract domain
domain = text.split("@")[1]
# Check if domain has valid format
domain_pattern = r"^[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
if not re.match(domain_pattern, domain):
return False
# Check for consecutive dots in domain
if ".." in domain:
return False
return True
email = "user@example.com"
result = is_email_with_domain_check(email)
print(result) # True
Notes
- Validates domain format
- Checks for domain issues
- No network lookup
- Fast validation
Email validation with local part rules¶
string email validation local part regex text
Email validation with local part specific rules
import re
def is_email_local_part_valid(text):
"""Email validation with local part specific rules."""
if not text or "@" not in text:
return False
local_part, domain = text.split("@", 1)
# Local part rules
if len(local_part) > 64:
return False
if local_part.startswith(".") or local_part.endswith("."):
return False
if ".." in local_part:
return False
# Check for valid characters in local part
local_pattern = r"^[a-zA-Z0-9._%+-]+$"
if not re.match(local_pattern, local_part):
return False
return True
email = "user.name+tag@example.com"
result = is_email_local_part_valid(email)
print(result) # True
email2 = ".user@example.com"
result2 = is_email_local_part_valid(email2)
print(result2) # False
Notes
- Validates local part format
- Checks length limits
- Handles special characters
- RFC compliant rules
Email validation with TLD check¶
string email validation tld domain text
Email validation with TLD format checking
import re
def is_email_with_tld_check(text):
"""Email validation with TLD (Top Level Domain) check."""
# Basic email validation
pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
if not re.match(pattern, text):
return False
# Extract TLD
domain = text.split("@")[1]
tld = domain.split(".")[-1]
# Check TLD length (2-6 characters)
if len(tld) < 2 or len(tld) > 6:
return False
# Check if TLD is alphabetic
if not tld.isalpha():
return False
return True
email = "user@example.com"
result = is_email_with_tld_check(email)
print(result) # True
email2 = "user@example.c"
result2 = is_email_with_tld_check(email2)
print(result2) # False
Notes
- Validates TLD format
- Checks TLD length
- Ensures alphabetic TLD
- More accurate validation
Email validation with common patterns¶
string email validation patterns regex text
Email validation checking for common invalid patterns
import re
def is_email_common_patterns(text):
"""Email validation checking for common invalid patterns."""
if not text or "@" not in text:
return False
# Check for common invalid patterns
invalid_patterns = [
r"^@", # Starts with @
r"@$", # Ends with @
r"@@", # Double @
r"\.@", # Dot before @
r"@\.", # Dot after @
r"\.\.", # Consecutive dots
r"^\.", # Starts with dot
r"\.$", # Ends with dot
]
for pattern in invalid_patterns:
if re.search(pattern, text):
return False
# Basic email pattern
email_pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
return bool(re.match(email_pattern, text))
email = "user@example.com"
result = is_email_common_patterns(email)
print(result) # True
email2 = "user@@example.com"
result2 = is_email_common_patterns(email2)
print(result2) # False
Notes
- Checks common invalid patterns
- Prevents obvious errors
- Comprehensive validation
- Useful for form validation
Email validation with length limits¶
string email validation length limits rfc text
Email validation with RFC compliant length limits
import re
def is_email_with_limits(text):
"""Email validation with RFC compliant length limits."""
if not text:
return False
# Total length check (RFC 5321)
if len(text) > 254:
return False
if "@" not in text:
return False
local_part, domain = text.split("@", 1)
# Local part length check (RFC 5321)
if len(local_part) > 64:
return False
# Domain length check
if len(domain) > 253:
return False
# Basic email pattern
pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
return bool(re.match(pattern, text))
email = "user@example.com"
result = is_email_with_limits(email)
print(result) # True
email2 = "a" * 65 + "@example.com"
result2 = is_email_with_limits(email2)
print(result2) # False
Notes
- RFC 5321 compliant limits
- Checks total, local, and domain lengths
- Prevents oversized emails
- Standards compliant
Email validation with case sensitivity¶
string email validation case sensitive text
Email validation with case sensitivity options
import re
def is_email_case_sensitive(text, case_sensitive=False):
"""Email validation with optional case sensitivity."""
if case_sensitive:
pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
else:
pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
text = text.lower()
return bool(re.match(pattern, text))
email = "User@Example.COM"
result = is_email_case_sensitive(email, case_sensitive=False)
print(result) # True
result2 = is_email_case_sensitive(email, case_sensitive=True)
print(result2) # True (same pattern, but case preserved)
Notes
- Optional case sensitivity
- Normalizes case if needed
- Flexible validation
- Useful for different requirements
🔗 Cross-References¶
- Reference: See 📂 Is URL
- Reference: See 📂 Validate Phone
🏷️ Tags¶
string, email, validation, regex, parse, text
📝 Notes¶
- Use regex for email validation
- Consider edge cases like subdomains and plus addressing
- Useful for input validation and user registration