Python course University of Heidelberg Summer 2026

Solutions Day 1 (March 30th)

03.01

[4**3,2+3.4**2,(1+1j)**2]

03.02

a = "... but a giant leap for mankind."
num=a.index('leap')
print(a[0:num]+a[num+4:])

03.03

s = "CAGTACCAAGTGAAAGAT"
s.count('A')

or maybe more cumbersome:

len(s.split(sep='A'))-1

a=[1,2,3]
b=[4,5,6]
c=a+b

# or

d=a
d.extend(b)
print (c,d)

04.01

x=3.7
(x>3.4 and x<=6.6) or (x==2)

04.02

dict={'snake':'Schlange','jungle':'Dschungel','lives':'lebt','in':'in','the':'der'}

s="The snake lives in the jungle"
for word in s.split():
    print (dict[word.lower()])

05.01

for i in range(2,1000):
    is_prime=True
    for j in range(2,i):
        if (i%j==0):
            is_prime=False
    if is_prime:
        print (i)
        

05.02: Simply break the loop since it is not necessary to search further if one divisor is found.

for i in range(2,1000):
    is_prime=True
    for j in range(2,i):
        if (i%j==0):
            is_prime=False
            break
    if is_prime:
        print (i)

05.03

# very terse:
a, b = 0, 1
while a < 100000:
    print(a)
    a, b = b, a + b

#Fibonacci sequence with index
#
l=[0]
i=0
x=1

while x<100000:
    l.append(x)     # add x_i
    x=l[i]+l[i+1]   # work out x_i+1
    i=i+1
    
print (len(l))

And the square Fibonaccis:

# determine square Fibonaccis
l=[0]
x=1

while x<100000:
    l.append(x)
    x=l[-2]+l[-1]

# print square Fibonacci numbers
for fibonacci in l:
    is_square=False
    for j in range(fibonacci):
        if j*j==fibonacci:
            is_square=True
            break
    if is_square:
        print ("square number =",fibonacci)

Solution Cryptography

s='pbatenghyngvbaf lbh unir fhpprrqrq va qrpelcgvat gur fgevat'

base=ord('a') # ascii code for 'a'
decode=-13
res=''
for character in s.lower():
    if character==' ':
        t=character
    else:
        ascii=ord(character)
        t=chr(((ascii+decode)-base)%26+base) # (ascii-97)%26 in range 0 ... 25
    res+=t
print (decode,res)   

The translation of ascii can also be done explicitly:

s='pbatenghyngvbaf lbh unir fhpprrqrq va qrpelcgvat gur fgevat'

base=ord('a') # ascii code for 'a'
decode=-13

res=''
for character in s.lower():
    if character==' ':
        tt=ord(' ')
    else:
        ascii=ord(character)
        tt=ascii+decode
        if tt>=base+26:
            tt-=26
        elif tt<base:
            tt+=26
    res+=chr(tt)
print (decode,res)

.... the same as a function: (functions are introduced on Tuesday)

def caesar_encrypt(message,shift):
    base=ord('a')
    res=''
    for character in message.lower():
        if character==' ':
            tt=ord(' ')
        else:
            ascii=ord(character)
            tt=ascii+shift
            if tt>=base+26:
                tt-=26
            elif tt<base:
                tt+=26
        res+=chr(tt)
    return res

caesar_encrypt(s,-13)

Determine the unkown cipher shift trying out all

s='wxkxmh ngynlcb cqn byjwrbq rwzdrbrcrxw'

for shift in range(-10,20):
    print (shift,caesar_encrypt(s,shift))

Note solution -9 and 17 are equivalent.