account.py

class Account:
    def __init__(self, login_name, password, uid, gid, user_name, directory, shell):
        self.login_name = login_name
        self.password = password
        self.uid = uid
        self.gid = gid
        self.user_name = user_name
        self.directory = directory
        self.shell = shell
    
def read(dateiname):
    accountliste = []
    try: 
        pwdatei = open(dateiname)
        for line in pwdatei.readlines():
            content = line.split(":")
            login_name = content[0]
            password = content[1]
            uid = content[2]
            gid = content[3]
            user_name = content[4]
            directory = content[5]
            shell =  content[6]
            new_acc = Account(login_name, password, uid, gid, user_name, directory, shell)
            accountliste.append(new_acc)
    except Exception: 
        print "line", content
        raise   
        print "Fehler bei Dateibehandlung"
    finally:    
        pwdatei.close()
    return accountliste
    
def find_account(liste, login_name):
    for account in liste:
        if login_name == account.login_name:
            return account
               
    raise KeyError

expr.py

# -*- coding: iso-8859-1 -*-
# Funktionen zur Darstellung von Ausdrücken entsprechend
# der Grammatik:
# epxr  = zahl | plus | minus | mal | durch
# plus  = expr '+' expr
# minus = expr '-' expr
# mal   = expr '*' expr
# durch = expr '/' expr
# Alle Ausdrücke werden durch Tupel repräsentiert:
# Zahlen durch 1-Tupel, binärde Operationen durch 3-Tupel
def zahl(n):
    return n,

def plus(a,b):
    return '+', a, b

def minus(a,b):
    return '-', a, b

def mal(a,b):
    return '*', a, b

def durch(a,b):
    return '/', a, b

def calc(expression):
    if len(expression) == 1:
        return expression[0]
    else:
        if expression[0] == "+":
            calculated = calc(expression[1]) + calc(expression[2]) 
        elif expression[0] == "-":
            calculated = calc(expression[1]) - calc(expression[2])
        elif expression[0] == "*":
            calculated = calc(expression[1]) * calc(expression[2])
        elif expression[0] == "/":
            calculated = float(calc(expression[1])) / float(calc(expression[2]))
        return calculated
        
def infix(expression, first = True):
    if len(expression) == 1:
        return str(expression[0])
    else:
        operation = infix(expression[1], False) + expression[0] + infix(expression[2], False)
        if not(first):
            operation = "("+ operation + ")"
        return operation

# 3*(4+5)
expr = mal(zahl(3), plus(zahl(4), zahl(5)))

print infix(expr),"=", calc(expr)

testfaelle.py

import account

liste = account.read("passwd")
#Vorbereitung  3. Testfall    
c = 0
for acc in liste:
    if acc.uid == "5131":
        c += 1

#Vorbereitung 5. Testfall    
try:
    account.find_account(liste, "billg")
    billgbool = False
except:
    billgbool = True

#assert-Block

assert liste[0].uid == "5316", "Erste UID ist nicht 5316."
assert liste[len(liste)-1].user_name == "Steffen Kensy", "Letzter Name ist nicht Steffen Kensy"
assert c == 1, "Es gibt mehr als einen Account mit der UID 5131"
assert account.find_account(liste, "fwesack").directory == "/home/stud/2005/fwesack", "User fwesack hat nicht /home/stud/2005/fwesack als Verzeichnis"
assert billgbool, 'find_account(liste, "billg") loest keine Ausnahme aus'

print "Erfolgreich."