Basics

Jupyter Notebook

Das Notebook tut aus Markdown HTML machen, und aus Python Code auch

print('hello world')

Syntax

for c in 'hello':
    print(c)

Batteries

import random
random.randrange(3, 7)

Tuple Unpacking

a, b = 1, 2

a

1

b

2

a, b = b, a

a

2

b

1

Ist das gleiche wie …

(a, b) = (b, a)

for

liste = [1, 'eins', 1.0]
for element in liste:
    print(element)

1
eins
1.0

In C: for (i=0; i<len(liste); i++) ...

Key Value Map

lookup_table = {
    'eins': 1,
    'zwei': 2,
    'drei': 3,
    # ...
}

lookup_table['eins']

1

lookup_table['vier'] = 4

lookup_table['vier']

4

try:
    lookup_table['fuenf']
except Exception as e:
    print(e)

'fuenf'

Syntax

Comments vs Documentation

# das ist ein kommentar

a = 1  # das ist auch ein kommentar

Docstrings

def do_something(some_number):
    "Das ist die Dokumentation von dieser Funktion do_something. Sie macht genau nichts, ausser deppert auf stdout auszuspucken"
    print('doing something with that number:', some_number)

do_something(42)

doing something with that number: 42

do_something.__doc__

'Das ist die Dokumentation von dieser Funktion do_something. Sie macht genau nichts, ausser deppert auf stdout auszuspucken'

help(do_something)

Help on function do_something in module __main__:

do_something(some_number)
    Das ist die Dokumentation von dieser Funktion do_something. Sie macht genau nichts, ausser deppert auf stdout auszuspucken

Multiline String (btw.)

def do_something(some_number):
    """Das ist die Dokumentation von dieser Funktion do_something.
    Sie macht genau nichts, ausser deppert auf stdout auszuspucken"""
    print('doing something with that number:', some_number)

do_something.__doc__

'Das ist die Dokumentation von dieser Funktion do_something.\n    Sie macht genau nichts, ausser deppert auf stdout auszuspucken'

help(do_something)

Help on function do_something in module __main__:

do_something(some_number)
    Das ist die Dokumentation von dieser Funktion do_something.
    Sie macht genau nichts, ausser deppert auf stdout auszuspucken

Variables

a = 42
a

42

type(a)

int

a = 'hallo'

type(a)

str

a = 42.666

type(a)

float

a = ['hallo', 666, 1.234]

type(a)

list

a

['hallo', 666, 1.234]

del a

try:
    a
except Exception as e:
    print(e)

name 'a' is not defined

a = 666

globals() is a function that returns a dictionary containing all global variables (nur so nebenbei)

globals()['a']

666

globals()['eine_neue_variable'] = ['hallo', 'welt', 42]

eine_neue_variable

['hallo', 'welt', 42]

Tuple Unpacking

a = 1
b = 2

Das geht auch anders:

a, b = 1, 2

Tuple?

(a, b) = (1, 2)

a, b

(1, 2)

Vertauschen von Variablen: klassisch

c = a
a = b
b = c
a, b

(2, 1)

a, b = 1, 2

a, b = b, a
a, b

(2, 1)

Assignment Details

a = 42
id(a)

140705292246608

b = a

id(b)

140705292246608

Datatypes

Numbers

Integer Numbers (Literals)

1234

1234

-1234

-1234

permission = 0o755

register_content = 0xdeadbeef
register_content

3735928559

register_content = 0b11010001110101000
register_content

107432

Arithmetic Operators

6/4

1.5

Python 2: 6/4 == 1. Erzwungen in Python 3: Floor Division

6//4

1

Modulo: Rest einer Division

6%4

2

7%3

1

6%3

0

i = 6
i = i+7
i

13

i = 6
i += 7
i

13

Wertebereich von Integers

10**6

1000000

10**10

10000000000

10**100

10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

hex(10**100)

'0x1249ad2594c37ceb0b2784c4ce0bf38ace408e211a7caab24308a82e8f10000000000000000000000000'

10**1000

10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

Die groesste Zahl, die auf 64 Bit darstellbar ist

i = 2**64-1
i

18446744073709551615

i += 1

i

18446744073709551616

Strings

s = 'abc'

s = "abc"

s = 'abc\'def'

s = "abc'def"

s = 'abc"def'

s = """erste zeile
zweite zeile"""
s

'erste zeile\nzweite zeile'

dos_path = 'C:\Programme\neues programm'
dos_path

'C:\\Programme\neues programm'

print(dos_path)

C:\Programme
eues programm

Raw Strings

dos_path = r'C:\Programme\neues programm'
print(dos_path)

C:\Programme\neues programm

Datatype Conversions

ein_string_der_aussieht_wie_ein_integer = '42'
type(ein_string_der_aussieht_wie_ein_integer)

str

ein_integer = int(ein_string_der_aussieht_wie_ein_integer)
ein_integer

42

type(ein_integer)

int

int(1.234)

1

Zur Basis 16 …

int('32', 16)

50

str(42)

'42'

str(24.234)

'24.234'

Complex Datatypes

Listen

l = []  # empty list

type(l)

list

l = list()
l

[]

l = ['hallo', 42, 1.5]
l

['hallo', 42, 1.5]

len(l)

3

l.append(True)
l

['hallo', 42, 1.5, True]

l.extend([1, 2, 3])
l

['hallo', 42, 1.5, True, 1, 2, 3]

l += ['vier', 5]
l

['hallo', 42, 1.5, True, 1, 2, 3, 'vier', 5]

Tuple? Wie Liste, nur immutable

t = ('eins', 2, 3.0)
t

('eins', 2, 3.0)

type(t)

tuple

Immutable: es gibt kein append() (und andere verändernde Methoden)

try:
    t.append(4)
except Exception as e:
    print(e)

'tuple' object has no attribute 'append'

Dictionaries

d = {}
type(d)

dict

d

{}

len(d)

0

d = dict()
d

{}

d = {
    'eins': 1,
    'zwei': 2,
}

len(d)

2

d['eins']

1

try:
    d['drei']    # KeyError: no such key
except KeyError as e:
    print(type(e), e)

<class 'KeyError'> 'drei'

value = d.get('drei')
print(value)

None

if d.get('drei') is None:
    print('nix drin')

nix drin

d['drei'] = 3
d['drei']

3

'drei' in d

True

del d['drei']   # delete key 'drei'