python oneliners

python.py

from IPython.terminal.prompts import Prompts, Token
class MyPrompt(Prompts):
    def in_prompt_tokens(self, cli=None):
        return [ ( Token.Prompt, "λ ",), ]
    def out_prompt_tokens(self, cli=None):
        return []
ip = get_ipython() # only in ipython
ip.prompts = MyPrompt(ip) # A minimal prompt for ipython

# Run external python file in blender
import bpy
import os
filename = os.path.join("D:/Documents/blender/modules/", "ut.py")
exec(compile(open(filename).read(), filename, 'exec'))

from subprocess import run, sys; run([sys.executable, '-m', 'pip', 'install', '<packagename>']) # install module from within python shell
from subprocess import run; run('pip install <packagename>', shell=True) # shorter version
from subprocess import run; run(['pip', 'install', '<packagename>']) # yes, shorter 
import os; f = os.path.join.(os.getcwd(), 'file.txt'); os.chmod(f, 0o600) # change file to rw for owner only
import psutil; psutil.Process().memory_info().rss/(1024 ** 2) # show memory size of running python shell in MB
import os; os.getcwd() # view current directory

import this # Zen of Python
import antigravity # You are flying! How?
os.environ['HOME'] # Get environment variable
os.environ.get('HOME') # sam, but different, but same
os.getenv('HOME') # Wrapper to os.environ.get('HOME')

with open('filename') as f:
    read_data = f.read()
with open('filename', 'w') as f:
    f.write("#First Line\n" + read_data) # insert at beginning of file
    
@classmethod # class method constructor with cls as parameter
@staticmethod # a static method with no arguments
@dataclass # define fields to include parameters/methods like __init__(), __repr__, ___eq___, some default to true already. Less typing

print("\033c", end='') # clear screen in REPL
 
# max() with lambda function as key parameter, list comprehension, str.split() and dict.get(), - before dict reverses order
max([word for word in 'Who is the richest, Bill Gates, Jeff Bezos, Warren Buffet, Mark Zuckerberg or Elon Musk?'.split()], 
    key=lambda k: {'Warren': 124.3, 'Bill': 132.3, 'Elon': 264.6, 'Jeff': 177.5, 'Mark': 75.2}.get(k,0))
   
import string; [ord(char) for char in string.ascii_uppercase] # show unicode code point values (order)

(lambda p: (w := [c.lower()for c in p if c.isalpha()]) == w[::-1])('') # palindrome checker, put string in last parenthesis
(lambda p: (w := [c.lower()for c in p if c.isalpha()]).__eq__(w[::-1]))('')
(lambda p: (w := [map(str.lower, (c for c in p if c.isalpha()))]) == w[::-1])('')

print("You have", coins:=5, f'coin{"s" if coins !=1 else ""}') # singular/plural
sum([num < 0 for num in [-1, -2, 3, 4]]) # occurencies of negative numbers
{str(n):n for n in range(1,11)} # generate dict of numbers with string of number as keys
{**{str(n):n for n in range(2,11)},'A': [11,1], 'K': 10, 'Q': 10, 'J': 10} # unpack dict into dict
{k: {'a':1, 'b':2, 'c':3, 'd':4}[k] for k in ['b','d']} # filter dict with keys in list
{{'a':1, 'b':2, 'c':3, 'd':4}[k] for k in ['b','d']} # just the values
[{'a':1, 'b':2, 'c':3, 'd':4}[k] for k in ['b','d','b']] # same key, multiple values to list
[i for i, c in enumerate(l) if c == 'x'] # list of index numbers in list l for every occurence of 'x'
[print("Fizz"*(i%3<1)+"Buzz"*(i%5<1)or i)for i in range(1,101)] # FizzBuzz oneliner, no output of list of None in script.
sum([100, 10, 20, 50, 30, 25][-i-1] * 1.03**i for i in range(6)) # Yearly Cashflows Future Value 3% p.a.
print('', end = '') # if you want to print 2 pandas series, without single space from newline in second series
a = b.copy(); a = b[:] # list.copy() and slicing when assign create new list. 
a[:] = [] # Changing list with slice doesn't create new list, assign without slice does
a = 1,2,3 # tuple without parenthesis
import importlib; importlib.reload(<module>) # reload module without leaving REPL
exit() # Stop script depends on site module
raise SystemExit # or raise SystemExit() exits script, does not depend on site module
a, b = [(1,2),(3,4)] # first tuple to a, second to b
a, b = zip(*[(1,2),(3,4)]) # first element of tuples to a, second to b
{'mus' : sum}['mus']((3,3)) # asign sum function as value of dict and calls it
{'' : print}['']('Hello world') # same
[print][0]('Hello world') # with list
(print,)[0]('Hello world') # as tuple
next(iter({print}))('Hallo World') # as set
[line.strip() for line in lines[:1]] # clean list elements from '\n', ommit header from csv list
g = (i for i in range(2,100)if all([i%j for j in range(2,i)])) # prime number generator to 100, next(g)
g = (lambda x: (i for i in range(2,x)if all([i%j for j in range(2,i)])))(100) # same, but with 100 as parameter
(lambda x: f'{x=}')(5) # 'x=5', debugging specifier
list(range(-5, 257)) # integers in this range are objects in Python
a=257;b=257;a is b # Optimized in Pyton interpreter but not in iPython 
(a := 'y'*4096) is (b :='y'*4096) # True, but not beyond, AST optimizer
'Go Sports! #Sports'.split('#')[1] # gives you the hashtag
a = (x for x in [1,2,3])
next(a, None) # finishes iteration with None instead StopIteration
import ast; print(ast.dump(ast.parse('{x for x in numbers}', mode='eval'), indent=4)) # check which expression, comprehension or object 

settings

# vscode
"pythonArgs": ["-i"], # launch.json, launches script in interactive console
"python.formatting.autopep8Args": ["--ignore=E731"], # settings.json, don't format my lambdas

set editing-mode vi in .inputrc, clear screen with ESC Ctrl-L in REPL

^Z, fg # go from python interpreter to bash and back again.

shell.sh

pylint.exe $(git ls-files '*.py') # Linting for all your python files in repository
ipython --TerminalInteractiveShell.editing_mode=vi # ipython with vim keybindings

pip freeze | %{$_.split('==')[0]} | %{pip install --upgrade $_} # update all packages in powershell

python -im pdb /dev/null # just start the python debugger
python -im pdb nul # same in powershell

youtube-dl -f bestvideo-bestaudio "url" # download best versions of your videos
pydoc <modulename> # offline documentation in the terminal like help() in the python shell

send2trash.exe # python programm that sends files to trash instead of deleting it permanently
python -m ensurepip # bootstrap pip installer
python -m site # show site-package directories
export API_KEY=***; python3 -c 'import os; print(os.environ["API_KEY"])' # Use enviroment variable in Python

jupyter nbconvert --execute --to markdown README.ipynb # convert notebook to markdown file

# Vim keybindings in Python interpreter
.vim.py:
import readline
readline.parse_and_bind('set editing-mode vim')
PYTHONSTARTUP=$HOME/.vim.py; export PYTHONSTARTUP