Calculate password strength.

PwStrength.py

# -*- coding: utf-8; -*-

# Calculate password strength.  Algorithm is based on the
# Wolfram|Alpha’s, without dictionary and “extra critira”.
#
# Darksair

# Usage: Strength = pwStrength(password).

import re

def findSeqChar(CharLocs, src):
    """Find all sequential chars in string `src'.  Only chars in
    `CharLocs' are considered. `CharLocs' is a list of numbers.  For
    example if `CharLocs' is [0,2,3], then only src[2:3] is a possible
    substring with sequential chars.
    """
    AllSeqChars = []
    i = 0
    SeqChars = []
    while i < len(CharLocs) - 1:
        if CharLocs[i + 1] - CharLocs[i] == 1 and \
               ord(src[CharLocs[i+1]]) - ord(src[CharLocs[i]]) == 1:
            # We find a pair of sequential chars!
            if not SeqChars:
                SeqChars = [src[CharLocs[i]], src[CharLocs[i+1]]]
            else:
                SeqChars.append(src[CharLocs[i+1]])
        else:
            if SeqChars:
                AllSeqChars.append(SeqChars)
                SeqChars = []

        i += 1
    if SeqChars:
        AllSeqChars.append(SeqChars)

    return AllSeqChars

def pwStrength(pw):
    """Wolfram|Alpha algorithm without dictionary and “extra critira”.
    """
    Score = 0
    Length = len(pw)
    Score += Length * 4
    # print("Length score: {}".format(Score))
    
    NUpper = 0
    NLower = 0
    NNum = 0
    NSymbol = 0
    LocUpper = []
    LocLower = []
    LocNum = []
    LocSymbol = []
    CharDict = {}
    
    for i in range(Length):
        Ch = pw[i]
        Code = ord(Ch)
        
        if Code >= 48 and Code <= 57:
            NNum += 1
            LocNum.append(i)
        elif Code >= 65 and Code <= 90:
            NUpper += 1
            LocUpper.append(i)
        elif Code >= 97 and Code <= 122:
            NLower += 1
            LocLower.append(i)
        else:
            NSymbol += 1
            LocSymbol.append(i)

        if not Ch in CharDict:
            CharDict[Ch] = 1
        else:
            CharDict[Ch] += 1

    if NUpper != Length and NLower != Length:
        if NUpper != 0:
            Score += (Length - NUpper) * 2
            # print("Upper case score:", (Length - NUpper) * 2)
        if NLower != 0:
            Score += (Length - NLower) * 2
            # print("Lower case score:", (Length - NLower) * 2)

    if NNum != Length:
        Score += NNum * 4
        # print("Number score:", NNum * 4)
    Score += NSymbol * 6
    # print("Symbol score:", NSymbol * 6)

    # Middle number or symbol
    Score += len([i for i in LocNum if i != 0 and i != Length - 1]) * 2
    # print("Middle number score:", len([i for i in LocNum if i != 0 and i != Length - 1]) * 2)
    Score += len([i for i in LocSymbol if i != 0 and i != Length - 1]) * 2
    # print("Middle symbol score:", len([i for i in LocSymbol if i != 0 and i != Length - 1]) * 2)

    # Letters only?
    if NUpper + NLower == Length:
        Score -= Length
        # print("Letter only:", -Length)
    if NNum == Length:
        Score -= Length
        # print("Number only:", -Length)

    # Repeating chars
    Repeats = 0
    for Ch in CharDict:
        if CharDict[Ch] > 1:
            Repeats += CharDict[Ch] - 1
    if Repeats > 0:
        Score -= int(Repeats / (Length - Repeats)) + 1
        # print("Repeating chars:", -int(Repeats / (Length - Repeats)) - 1)

    if Length > 2:
        # Consequtive letters
        for MultiLowers in re.findall(''.join(["[a-z]{2,", str(Length), '}']), pw):
            Score -= (len(MultiLowers) - 1) * 2
            # print("Consequtive lowers:", -(len(MultiLowers) - 1) * 2)
        for MultiUppers in re.findall(''.join(["[A-Z]{2,", str(Length), '}']), pw):
            Score -= (len(MultiUppers) - 1) * 2
            # print("Consequtive uppers:", -(len(MultiUppers) - 1) * 2)
        
        # Consequtive numbers
        for MultiNums in re.findall(''.join(["[0-9]{2,", str(Length), '}']), pw):
            Score -= (len(MultiNums) - 1) * 2
            # print("Consequtive numbers:", -(len(MultiNums) - 1) * 2)
        
        # Sequential letters
        LocLetters = (LocUpper + LocLower)
        LocLetters.sort()
        for Seq in findSeqChar(LocLetters, pw.lower()):
            if len(Seq) > 2:
                Score -= (len(Seq) - 2) * 2
                # print("Sequential letters:", -(len(Seq) - 2) * 2)
        
        # Sequential numbers
        for Seq in findSeqChar(LocNum, pw.lower()):
            if len(Seq) > 2:
                Score -= (len(Seq) - 2) * 2
                # print("Sequential numbers:", -(len(Seq) - 2) * 2)

    return Score

Consider it under WTFPL :-).

Perfect. :-) My PHP port is here: https://gist.github.com/2926619 (for anyone interested).