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Fix: enforce first char is letter in validate_user() (Closes #1) #37262

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Fix: enforce first char is letter in validate_user() (Closes #1) #37262

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15 changes: 15 additions & 0 deletions Course3/Lab4/validations.py
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
#!/usr/bin/env python3

#!/usr/bin/env python3

import re

def validate_user(username, minlen):
Expand All @@ -12,13 +14,26 @@ def validate_user(username, minlen):
# Usernames can't be shorter than minlen
if len(username) < minlen:
return False

# ✅ First character must be a letter
if not username[0].isalpha():
return False

# Usernames can only use letters, numbers, dots and underscores
if not re.match('^[a-z0-9._]*$', username):
return False

# Usernames can't begin with a number
if username[0].isnumeric():
return False

return True


# Test cases
print(validate_user("blue.kale", 3)) # True
print(validate_user(".blue.kale", 3)) # False
print(validate_user("red_quinoa", 4)) # True
print(validate_user("_red_quinoa", 4)) # False