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10,440 PointsBoolean with re?
Hey. Can you help please with the following. Using RE, I want to check a string, which is meant to be a passwords. True if it contains >= 10 chars, at least one lower letter, one capital letter and one number; else False. How would a code look like. Thanks.
e.g. two cases:
True = 'bAse730onE4'
False = 'saaaa90'
re.match('[a-zA-Z0-9]+', password)
3 Answers
Chris Freeman
Treehouse Moderator 68,441 PointsBecause you are looking for the AND
of multiple conditions there isn't a short single concise regexp that will solve your needs because your conditions are not order dependent. That is, you would have to check for all combinations of a condition followed by all others. For example lowercase followed by uppercase followed by number and being 10 characters long, plus the other 5 combinations, OR
ed together in a single regexp.
The other option is to create the 3 search patterns and check that they each match plush a length check.
patterns = []
patterns.append(re.compile(r'[a-z]+')) #lowercase
patterns.append(re.compile(r'[A-Z]+')) #uppercase
patterns.append(re.compile(r'[0-9]+') )# number
password_good = True
if len(password_string) < 10:
password_good = False
else:
for pat in patterns:
if not pat.search(password_string):
# pattern not found
password_good = False
break
You could include the length check as a regexp:
patterns.append(re.compile(r'\w{10,}'))
I'll work on the combined uber-regexp to show it's complications and ammend my answer.
EDIT: Here is a single regexp pattern to match against. Yeah, it's not pretty:
In [101]: patx = re.compile(r'''
\w*[a-z]+\w*[A-Z]+\w*[0-9]+\w*|
\w*[a-z]+\w*[0-9]+\w*[A-Z]+\w*|
\w*[A-Z]+\w*[a-z]+\w*[0-9]+\w*|
\w*[A-Z]+\w*[0-9]+\w*[a-z]+\w*|
\w*[0-9]+\w*[a-z]+\w*[A-Z]+\w*|
\w*[0-9]+\w*[A-Z]+\w*[a-z]+\w*
''', re.X)
In [102]: patx.search("")
In [103]: patx.search("a")
In [104]: patx.search("aA1")
Out[104]: <_sre.SRE_Match object; span=(0, 3), match='aA1'>
Now you can use:
if not len(password) > 10 and patx.search(password)
print("Bad Password")
Tatiana Jamison
6,188 PointsHi Igor, re.search and re.match return match objects. If the item isn't found, it returns None (the special value). re.match checks for a match at the beginning of the string, whereas re.search checks anywhere in the string. You can use the boolean operator "and" to check multiple conditions--for example:
def check_two(string):
return re.search(\w+) and re.search(\d+)
returns True if the string contains at least one word character ([a-zA-Z0-9_]) and at least one decimal digit. You can get more specific by using a set definition, like [a-z]+.
igsm '
10,440 PointsThank you. Really helpful!
Chris Freeman
Treehouse Moderator 68,441 PointsChris Freeman
Treehouse Moderator 68,441 PointsAdded uber-regexp to answer.
If switching to
re.match
instead of search, use thepatx
as above:re.match(patx, password)
If you choose to switch to
re.search
, you can remove the leading and trailing\w*
from each line in thepatx
regexp.Tatiana Jamison
6,188 PointsTatiana Jamison
6,188 PointsThis works, too:
Technically, it actually returns None when the password is bad, but that's fine in a lot of applications. Easy modification if the False return is important: