NBA_03_Generatoren

(c) 2023 Technische Hochschule Augsburg - Fakultät für Informatik - Prof.Dr.Nik Klever - Impressum

Generatoren

Rückgabewert: wird statt mit return mit yield zurückgegeben

def reverse(data):
    for index in range(len(data)-1, -1, -1):
        yield data[index]
        
for char in reverse("golf"):
    print(char)

f
l
o
g

gen = reverse("01234")
gen

<generator object reverse at 0x7ff5584b90f8>

next(gen)

'4'

next(gen)

'3'

next(gen)

'2'

next(gen)

'1'

next(gen)

'0'

next(gen)

---------------------------------------------------------------------------
StopIteration                             Traceback (most recent call last)
<ipython-input-8-8a6233884a6c> in <module>()
----> 1 next(gen)

StopIteration: 

Rückblick: List Comprehension

lc = [x for x in range(10) if x%2 == 0]
lc

[0, 2, 4, 6, 8]

Generator Ausdruck

ga = (x for x in range(10) if x%2 == 0)
ga

<generator object <genexpr> at 0x7ff5584c73b8>

for i in ga:
    print(i)

0
2
4
6
8

s = sum(x for x in range(10) if x%2 == 0)
s

20

from math import pi, sin
sinus_tabelle = {x:sin(x*pi/180) for x in range(0,46)}
sinus_tabelle

{0: 0.0,
 1: 0.01745240643728351,
 2: 0.03489949670250097,
 3: 0.05233595624294383,
 4: 0.0697564737441253,
 5: 0.08715574274765817,
 6: 0.10452846326765346,
 7: 0.12186934340514748,
 8: 0.13917310096006544,
 9: 0.15643446504023087,
 10: 0.17364817766693033,
 11: 0.1908089953765448,
 12: 0.20791169081775931,
 13: 0.224951054343865,
 14: 0.24192189559966773,
 15: 0.25881904510252074,
 16: 0.27563735581699916,
 17: 0.29237170472273677,
 18: 0.3090169943749474,
 19: 0.32556815445715664,
 20: 0.3420201433256687,
 21: 0.35836794954530027,
 22: 0.374606593415912,
 23: 0.3907311284892737,
 24: 0.40673664307580015,
 25: 0.42261826174069944,
 26: 0.4383711467890774,
 27: 0.45399049973954675,
 28: 0.4694715627858908,
 29: 0.48480962024633706,
 30: 0.49999999999999994,
 31: 0.5150380749100542,
 32: 0.5299192642332049,
 33: 0.5446390350150271,
 34: 0.5591929034707469,
 35: 0.573576436351046,
 36: 0.5877852522924731,
 37: 0.6018150231520483,
 38: 0.6156614753256582,
 39: 0.6293203910498374,
 40: 0.6427876096865393,
 41: 0.6560590289905072,
 42: 0.6691306063588582,
 43: 0.6819983600624985,
 44: 0.6946583704589973,
 45: 0.7071067811865475}

for i in sinus_tabelle:
    print(i)

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45

from pygal import XY
from IPython.display import SVG
sinus_tabelle_als_liste = [(x,sin(x*pi/180)) for x in range(0,361)]
xy = XY()
xy.add("y=sin(x*pi/180)", sinus_tabelle_als_liste)
SVG(xy.render())

Zusammenfassung

Generator Ausdruck

line_liste = ["   line 1\n", "line 2   \n", "\n"]

stripped_generator = (line.strip() for line in line_liste)
stripped_generator

<generator object <genexpr> at 0x7ff54ac7ddb0>

for x in stripped_generator:
    print("<{}>".format(x))

<line 1>
<line 2>
<>

List Comprehension

stripped_list = [line.strip() for line in line_liste]
stripped_list

['line 1', 'line 2', '']

seq1 = "abc"
seq2 = (1,2,3)
z = [(x,y) for x in seq1 for y in seq2]
z

[('a', 1),
 ('a', 2),
 ('a', 3),
 ('b', 1),
 ('b', 2),
 ('b', 3),
 ('c', 1),
 ('c', 2),
 ('c', 3)]

[x,y for x in seq1 for y in seq2]

  File "<ipython-input-23-9fc9191dedc1>", line 1
    [x,y for x in seq1 for y in seq2]
           ^
SyntaxError: invalid syntax

Binärbaum

def inorder(t):
    if t:
        for x in inorder(t.left):
            yield x
            
        yield t.label
        
        for x in inorder(t.right):
            yield x

class Tree:
    
    def __init__(self, label, left=None, right=None):
        self.label = label
        self.left = left
        self.right = right
        
    def __repr__(self, level=0, indent="    "):
        s = level*indent + repr(self.label)
        if self.left:
            s += "\n" + self.left.__repr__(level+1, indent)
        if self.right:
            s += "\n" + self.right.__repr__(level+1, indent)
        return s
    
    def __iter__(self):
        return inorder(self)

def tree(list):
    n = len(list)
    if n == 0:
        return []
    i = n // 2
    return Tree(list[i], tree(list[:i]), tree(list[i+1:]))

t = tree("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
print(t)

'N'
    'G'
        'D'
            'B'
                'A'
                'C'
            'F'
                'E'
        'K'
            'I'
                'H'
                'J'
            'M'
                'L'
    'U'
        'R'
            'P'
                'O'
                'Q'
            'T'
                'S'
        'X'
            'W'
                'V'
            'Z'
                'Y'

for x in t:
    print(x,end="")

ABCDEFGHIJKLMNOPQRSTUVWXYZ

Übergabe von Parameter an Generatoren

def counter(maximum):
    i = 0
    while i < maximum:
        val = (yield i)
        if val is not None:
            i = val
        else:
            i += 1

gen = counter(10)
gen

<generator object counter at 0x7ff55fd34db0>

next(gen)

0

next(gen)

1

gen.send(8)

8

next(gen)

9

next(gen)

---------------------------------------------------------------------------
StopIteration                             Traceback (most recent call last)
<ipython-input-40-8a6233884a6c> in <module>()
----> 1 next(gen)

StopIteration: