human
Solve in Python:
# Do you ever wish you could talk like Siegfried of KAOS ?

## YES, of course you do!

https://en.wikipedia.org/wiki/Get_Smart


# Task

Write the function ```siegfried``` to replace the letters of a given sentence.

Apply the rules using the course notes below. Each week you will learn some more rules.

Und by ze fifz vek yu vil be speakink viz un aksent lik Siegfried viz no trubl at al!

# Lessons

## Week 1

* ```ci``` -> ```si```
* ```ce``` -> ```se```
* ```c``` -> ```k``` (except ```ch``` leave alone)

## Week 2

* ```ph``` -> ```f```

## Week 3

* remove trailing ```e``` (except for all 2 and 3 letter words)
* replace double letters with single letters (e.g. ```tt``` -> ```t```)

## Week 4

* ```th``` -> ```z```
* ```wr``` -> ```r```
* ```wh``` -> ```v```
* ```w``` -> ```v```

## Week 5

* ```ou``` -> ```u```
* ```an``` -> ```un```
* ```ing``` -> ```ink``` (but only when ending words)
* ```sm``` -> ```schm``` (but only when beginning words)


# Notes

* You must retain the case of the original sentence
* Apply rules strictly in the order given above
* Rules are cummulative. So for week 3 first apply week 1 rules, then week 2 rules, then week 3 rules
 ... Can you provide a the Python program you requested?
assistant
#Here is the Python program you requested.

import re
def siegfried(week, txt):
    if week == 1:
        txt = re.sub('ci', matchcase('si'), txt, flags=re.I)
        txt = re.sub('ce', matchcase('se'), txt, flags=re.I)
        txt = re.sub('(?!ch)[c]', matchcase('k'), txt, flags=re.I)
    elif week == 2:
        txt = siegfried(1, txt)
        txt = re.sub('ph', matchcase('f'), txt, flags=re.I)
    elif week == 3:
        txt = siegfried(2, txt)
        txt = re.sub(r'(?<=\w{3})e\b', '', txt)
        txt = re.sub(r'([a-z])\1', r'\1', txt, flags=re.I)
    elif week == 4:
        txt = siegfried(3, txt)
        txt = re.sub('th', matchcase('z'), txt, flags=re.I)
        txt = re.sub('wr', matchcase('r'), txt, flags=re.I)
        txt = re.sub('wh|w', matchcase('v'), txt, flags=re.I)
    elif week == 5:
        txt = siegfried(4, txt)
        txt = re.sub('ou', 'u', txt)
        txt = re.sub('an', matchcase('un'), txt, flags=re.I)
        txt = re.sub(r'ing\b', matchcase('ink'), txt, flags=re.I)
        txt = re.sub(r'\bsm', matchcase('schm'), txt, flags=re.I)
    return txt
    
def matchcase(word):
        def replace(m):
            text = m.group()
            if text.isupper():
                return word.upper()
            elif text.islower():
                return word.lower()
            elif text[0].isupper():
                return word.capitalize()
            else:
                return word
        return replace