Compound Datatypes

Dictionary

d = {}

len(d)

0

d = {
    11: 'Simmering',
    1: 'Innere Stadt',
}

len(d)

2

d[11]

'Simmering'

d[5] = 'Keine Ahnung'
len(d)

3

d[5]

'Keine Ahnung'

11 in d

True

'Simmering' in d

False

Iteration

d

{11: 'Simmering', 1: 'Innere Stadt', 5: 'Keine Ahnung'}

for element in d:
    print(element)

11
1
5

for key in d.keys():
    print(key)

11
1
5

for value in d.values():
    print(value)

Simmering
Innere Stadt
Keine Ahnung

for item in d.items():
    print(item)

(11, 'Simmering')
(1, 'Innere Stadt')
(5, 'Keine Ahnung')

for item in d.items():
    key = item[0]
    value = item [1]
    print(f'key: {key}, value: {value}')

key: 11, value: Simmering
key: 1, value: Innere Stadt
key: 5, value: Keine Ahnung

for key, value in d.items():
    print(f'key: {key}, value: {value}')

key: 11, value: Simmering
key: 1, value: Innere Stadt
key: 5, value: Keine Ahnung

Set

s = set()
len(s)

0

s.add(1)
s.add('Joerg')
len(s)

2

'Joerg' in s

True

'Christopher' in s

False

s.remove('Joerg')

'Joerg' in s

False

Iteration

s = { 1, 2, 3, 4, 5}

s

{1, 2, 3, 4, 5}

for element in s:
    print(element)

1
2
3
4
5

List

l = [1, 2, 3, 'vier']

len(l)

4

1 in l

True

3 in l

True

'vier' in l

True

Iterable?

l = [1, 2, 3, 'vier']
for element in l:
    print(element)

1
2
3
vier

s = set(l)
s

{1, 2, 3, 'vier'}

mein_string = 'joerg'
for element in mein_string:
    print(element)

j
o
e
r
g

s = set(mein_string)
s

{'e', 'g', 'j', 'o', 'r'}

for element in s:
    print(element)

g
j
e
o
r

'g' in s

True

The range() Function

i = 1
while i <=10:
    print(i)
    i += 1

1
2
3
4
5
6
7
8
9
10

l = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
for element in l:
    print(element)

1
2
3
4
5
6
7
8
9
10

for element in range(1, 11):
    print(element)

1
2
3
4
5
6
7
8
9
10

for element in range(0, 10, 2):
    print(element)

0
2
4
6
8

for element in range(10):
    print(element)

0
1
2
3
4
5
6
7
8
9

r = range(3)

for element in r:
    print(element)

0
1
2

type(r)

range

it = iter(r)

type(it)

range_iterator

next(it)

0

next(it)

1

next(it)

2

try:
    next(it)
except StopIteration:
    pass

for element in range(3):
    print(element)

0
1
2

List Comprehension, Generator Expression

def squares(iterable):
    sq = []
    for elem in iterable:
        sq.append(elem**2)
    return sq
for elem in squares([0,1,2,3,4]):
    print(elem)

0
1
4
9
16

for elem in [i**2 for i in [0,1,2,3,4]]:
    print(elem)

0
1
4
9
16

for elem in [i**2 for i in range(5)]:
    print(elem)

0
1
4
9
16

Generator expression:

for elem in (i**2 for i in range(5)):
    print(elem)

0
1
4
9
16

for elem in (i**2 for i in range(10) if i%2==0):
    print(elem)

0
4
16
36
64

Strings

Literals

'Hello'

'Hello'

"Hello"

'Hello'

Quoting?

'Hello \'World\''

"Hello 'World'"

"Hello 'World'"

"Hello 'World'"

Embedded Newline Character

docu = 'Das ist eine \nmehrzeilige Dokumentation\nvon irgendwas'
print(docu)

Das ist eine
mehrzeilige Dokumentation
von irgendwas

Multiline Strings

docu = '''Das ist eine
mehrzeilige Dokumentation
von irgendwas'''
print(docu)

Das ist eine
mehrzeilige Dokumentation
von irgendwas

Raw Strings

Man hat Files mit folgendem deppertem Inhalt:

line = 'irgendein irrelevanter quargel, Joerg, Faschingbauer, 190666'

Lösung: regular expressions

import re
pattern = re.compile(r'^.*, (\w+), (\w+), (\d+)')

match = pattern.search(line)

if match is None:
    print('Inkorrekte Zeile')
else:
    print('Vorname:', match.group(1), 'Nachname:', match.group(2), 'Geburtsdatum:', match.group(3))

Vorname: Joerg Nachname: Faschingbauer Geburtsdatum: 190666

Functionality

s = 'Hello World'

s.capitalize()

'Hello world'

s = s.capitalize()

s

'Hello world'

s.center(50)

'                   Hello world                    '

'mississippi'.count('ss')

2

'ein-excel-export.csv'.endswith('.csv')

True

'mississippi'.find('ss')

2

'mississippi'.find('sss')

-1

'mississippi'.index('ss')

2

try:
    'mississippi'.index('sss')
except ValueError:
    print('not found')

not found

'abc'.isalpha()

True

'abc'.isidentifier()

True

'123'.isidentifier()

False

'123'.isidentifier()

False

'abc'.islower()

True

'ABC'.islower()

False

'-'.join(['Hello', 'World'])

'Hello-World'

'arg1,arg2,arg3'.split(',')

['arg1', 'arg2', 'arg3']

strip() and friends

'  blah blah  \t\n   '.strip()

'blah blah'

'abcblah blahabcbcabcc'.strip('abc')

'lah blah'

'   abc    '.rstrip()

'   abc'

'   abc    '.lstrip()

'abc    '

String Formatting

'Hello {0} {1}'.format('World', 666)

'Hello World 666'

'Hello {was} {wieviel}'.format(wieviel=666, was='World')

'Hello World 666'

'Hello {was:<10} {wieviel}'.format(wieviel=666, was='World')

'Hello World      666'

f-Strings (since Python 3.6)

wieviel = 666
was = 'Hello'

f'Hello {was} {wieviel}'

'Hello Hello 666'

f'Hello {was:<10} {wieviel}'

'Hello Hello      666'

datetime

import datetime

now = datetime.datetime(2021, 7, 11, 23, 11, 33)
now

datetime.datetime(2021, 7, 11, 23, 11, 33)

delta = datetime.timedelta(days=3, seconds=39)
delta

datetime.timedelta(days=3, seconds=39)

now + delta

datetime.datetime(2021, 7, 14, 23, 12, 12)

now - delta

datetime.datetime(2021, 7, 8, 23, 10, 54)

now = datetime.datetime.now()
now

datetime.datetime(2021, 8, 25, 15, 3, 10, 995237)

Parsing date formats

datestr = '11.07.2021'

dt = datetime.datetime.strptime(datestr, '%d.%m.%Y')
dt

datetime.datetime(2021, 7, 11, 0, 0)

JSON

import json
import uuid

Create a message object to, for example, transfer it via MQTT

msg_aussi = {
    'message': 'seas oida',
    'msgid': uuid.uuid4().hex,
    'timestamp': 345654325678,
}

Convert it to JSON for the transfer

json_aussi = json.dumps(msg_aussi)
json_aussi

'{"message": "seas oida", "msgid": "6563515ef0824d42b459389cefd09127", "timestamp": 345654325678}'

Transfer it

json_eini = json_aussi

Convert JSON back to dictionary that the sender had, originally

msg_eini = json.loads(json_eini)
msg_eini

{'message': 'seas oida',
 'msgid': '6563515ef0824d42b459389cefd09127',
 'timestamp': 345654325678}