Python and Libraries Cheatsheet

Sum

sum(<list>)

Profile

import pycallgraph
graph = pycallgraph.output.GraphvizOutput()
graph.output_file = <filename>
whith pycallgraph.PyCallGraph(output=graph):
    <code>

SQLite

import sqlite3
db = sqlite3.connect(<filename>)

Read

cursor = db.execute(<query>)
if cursor:
    cursor.<fetchone/fetchall>()
db.close()

Write

db.execute(<query>)
db.commit()

Curses

import curses
def main():
    curses.wrapper(draw)
def draw(screen):
    screen.clear()
    screen.addstr(0, 0, "Press ESC to quit.")
    while screen.getch() != 27:
        pass

Regex

import re
re.sub(<regex>, <new>, <text>)
re.search(<regex>, <text>)

Threading

import threading

Thread

thread = threading.Thread(target=<function>, args=(<first arg>, ))
thread.start()
thread.join()

Lock

lock = threading.Rlock()
lock.acquire()
lock.release()

Bottle

import bottle

Run

bottle.run(host='localhost', port=8080)
bottle.run(host='0.0.0.0', port=80, server='cherypy')

Static request

Dynamic request

REST request

Type

type(<el>) is int/str/set/list

import numbers
isinstance(<el>, numbers.Number)

Arguments

import sys
sys.argv

Enumerate

for i, <el> in enumerate(<list>)

System Commands

Read File

with open(<filename>, encoding='utf-8') as file:
    return file.readlines()

Write to File

with open(<filename>, 'w', enconding='utf-8') as file:
    file.write(<text>)

Execute Command

import os
os.popen(<command>).read()

JSON

import json

Read File

with open(<filename>, encoding='utf-8') as file:
    return json.load(file)

Write to File

with open(<filename>, 'w', enconding='utf-8') as file:
    file.write(json.dumps(<object>))

Datetime

import datetime
now = datetime.datetime.now()
now.strftime('%Y%m%d')
now.strftime('%Y%m%d%H%M%S')

String

str.replace(<text>, <old>, <new>)
<str>.isnumeric()

Enum

import enum
class <name>(enum.Enum):
    <value> = <index>

Copy

import copy
copy.copy(<object>)
copy.deepcopy(<object>)

Infinity

float("inf")

Plot

import matplotlib
matplotlib.pyplot.plot(<data>, ...)
matplotlib.pyplot.show()
matplotlib.pyplot.savefig(<filename>)

List

<list>[<inclusive from>:<exclusive to>:<step size>]

Lambda

lambda <arg1>, <arg2>: <return value>
lambda: <return value>

[For]

[i+1 for i in range(10)]
[i+1 for i in range(10) if i > 5]
[i+j for i in range(10) for j in range(10)]

Class

class <name>:
    def __init__(self, <arg>):
        self.a = <arg>
    def __repr__(self):
        return str({'a': self.a})
    def __str__(self):
        return str(self.a)

Random

import random
random.random()
random.randint(<from inclusive>, <to inclusive>)
random.shuffle(<list>)

Range

range(<to exclusive>)
range(<from inclusive>, <to exclusive>)
range(<from inclusive>, <to exclusive>, <step size>)  # Negative step for backward

List

<list>.sort()
<list>.reverse()
<list>.extend(<list>)

Print

print(<el1>, <el2>, end='', sep='', file=<file>)

Format

'{}'.format(<el>)

{:<min width>}  -> '<el>    '
{:><min width>} -> '    <el>'
{:^<min width>} -> '  <el>  '
{:_<min width>}  -> '<el>____'
{:.<max width>} -> '<e>'
{:<max widht>.<min width>} -> '    <e>'
{:<max width>.<no of decimals>f} -> '  3.14'

Text Wrap

import textwrap
textwrap.wrap(<text>, <width>)

Dictionary

.items() .get(, ) .setdefault(, )