Python  Cheat Sheet

Die folgenden Texte dienen nur als Gedächtnisstütze für fortgeschrittene Leser, die sie ohne weitere Erklärung verstehen.

Listen

l = list()
l = []
l.append( item )
item in l
l.index( term )
print( l )

Listen append

l = []; l.append( [ 0, 1, 2 ]); print( l )

[[0, 1, 2]]

l = []; l.append( 'abc' ); print( l )

['abc']

Listen +=

l = []; l +=[ 0, 1, 2 ]; print( l )

[0, 1, 2]

l = []; l += 'abc'; print( l )

['a', 'b', 'c']

Zuordnungen

d = dict()
d[ key ]= value
print( d )
for key in dict:

Installieren

https://pypi.org/search/?q=example
py -m pip install pywin32-224-cp37-cp37m-win_amd64.whl
ungzip example.tar.gz; cd example; py setup.py install 
ungzip example.tar.gz; cd example; py ez_setup.py

Schlafen

__import__( "time" ).sleep( 1 )

Zeitstempel (Uhrzeit und Datum, Stampade)

__import__( "datetime" ).datetime.now().replace( microsecond=0 ).isoformat( 'T' )

Jahr und Monat

current=__import__( "datetime" ).datetime.now().strftime('%Y-%m')

Zeitrechnen (was ist in 11 Tagen und 2 Stunden?)

__import__( "datetime" ).datetime.now()+__import__( "datetime" ).timedelta(days=11,hours=2)

Dezimalzahlen

__import__( "decimal" ).Decimal( 1 / 10 )

Zufallszahlen

__import__( "random" ).random()
__import__( "random" ).randint( 0, 2 ) 
__import__( "random" ).choice( [ 'heads', 'tails' ])

Aktuelles Verzeichnis

__import__( "os" ).getcwd()
__import__( "os" ).chdir( 'C:/example' )

Suchen und Ersetzen

__import__( "re" ).sub( r'(b)', r'[\1\1]', 'abcabbc' )

Unterprozesse

subprocess.check_call( [ sys.executable, 'hello.py'])
subprocess.check_call( [ sys.executable, '-m', 'pip', 'install', 'numpy'])
subprocess.Popen(['start', 'hello.txt'], shell=True)

Unterprozesse (ungetestet)

args = [ sys.executable, '-m', 'pip', 'install', 'numpy' ]
command=__import__( 'subprocess' ).list2cmdline(args)
print( f'EXECUTING {command}' )
with __import__( 'subprocess' ).Popen \
( command, 
  stdout=__import__( 'subprocess' ).PIPE, 
  stderr=__import__( 'subprocess' ).STDOUT, 
  bufsize=1, universal_newlines=True) as p:
    for line in p.stdout:
        print( end=line )
print( 'returncode = ', p.returncode )

execfile

def execfile( filename ):
    assert( type( filename )== type( '' ))
    file = open( filename, 'rb' )
    contents = file.read()
    del file
    compiled = compile( contents, filename, 'exec' )
    del contents
    del filename
    exec( compiled )
    del compiled

exceptions

except Exception as inst:
       print( sys.exc_info()[ 0 ])
       print( type( inst ))
       print( inst.args )
       print( inst )

Python-Version

__import__( "sysconfig" ).get_python_version()
__import__( "sys" ).version

Logging

import logging
logger = logging.getLogger()
handler = logging.StreamHandler()
formatter = logging.Formatter( '%(asctime)s %(name)-12s %(levelname)-8s %(message)s' )
handler.setFormatter( formatter )
logger.addHandler( handler )
logger.setLevel( logging.DEBUG )
logger.debug( 'example' )

Super aufrufen

super().__init__( *args, **kwargs ):

Nicht portabel, nur CPython  (Stand 2018)

__import__( "inspect" ).currentframe().f_back.f_locals[ 'a' ]
__import__( "inspect" ).currentframe().f_back.f_globals[ 'a' ] 

Quellcode

bltinmodule.c
bltinmodule.c.h
unicodeobject.h