PCAP-31-0x Cheat Sheet

Time Module - asctime() and mktime() functions

import time

timestamp = 1572879180
st = time.gmtime(timestamp)

print(time.asctime(st))
print(time.mktime((2019, 11, 4, 14, 53, 0, 0, 308, 0)))

Import Modules

import math

import sys

import math, sys

from math import pi

from math import pi, sin

import math as m

from math import pi as p

from math import pi as PI, sin as sinus

Working with modules

dir()

list all entities within a module

Random Module

from random import seed	seed(a=None, version=2) - initializes random number generator, a=None current time used
from random import random	random() - random float ranging 0.0<= X < 1.0
from random import randrange	randrange(start, stop[, step])
from random import randint	randint(a, b) - a <= N <= b. Alias for randrange(a, b+1)
from random import choice	choice(seq) - return random element
from random import sample	sample(population, k, *, counts=None) - return list of elements

Platform Module

from platform import platform	platform(aliased=0, terse=0) - returns single stringe showing underlying platform
from platform import machine	machine() - return machine type e. g. 'AMD64'
from platform import processor	processor() - return real processor name 'amdk6'
from platform import system	system() - return OS name e. g. 'Windows', 'Linux'
from platform import version	version() - return system release
from platform import python_implementation	python_implementation() - return python version as string 'major.minor.patchlevel'

Sorting

sorted()	new list gets created
sort()	performed in situ, changes the original list

OOP - check attributes

class Sampleclass:
    a = 1
    def __init__(self):
        self.b = 2
 
 
object = Sampleclass()
 
print(hasattr(object , 'b'))
print(hasattr(object , 'a'))
print(hasattr(Sampleclass, 'b'))
print(hasattr(Sampleclass, 'a'))

OOP - class variable

class Sampleclass:
    counter = 0
    def __init__(self, var = 1):
        self.__first = var
        Sampleclass.counter += 1

OOP - instance variable

class Sampleclass:
    def __init__(self, var = 1):
        self.first = var

    def set_second(self, var):
        self.second = var

Object Oriented Programming (OOP) - general

class is a set of objects

objects belongs to a class

object is incarnation of requirements, properties, qualities of a class

OOP - Method Vars

class Sample:
    varia = 2
    def method(self):
        print(self.varia, self.var)


obj = Sample()
obj.var = 3
obj.method()

OOP - Method Resolution Order (MRO)

Way a language scans through the upper part of classes
class Bottom(Middle, Top)	works when Top created before Middle
class Bottom(Top, Middle)	fails when Top created before Middle

OOP - Vars (some)

__dict__	shows entities
__name__	name of class
__module__	name of module
__bases__	names of direct superclasses

OOP - Sub/Superclass and Incarnation

issubclass()	identifies relationship between 2 classes
	each class considers itself to be a subclass of itself
isinstance()	Checks if object is an incarnation of a class

"Is" operator

checks whether two variables refer to the same object

variables don't store the object, they point to internal Python memory

OOP - Inheritance with more than one class

class Sub(Left, Right)	Python scans left to right
	if vars duplicate, "Left" vars will be shown

Generators and Iterators - general

Generator produce a series of values and control iteration process (range())

Iterator is an object conforming to iterator protocol (__iter__(), __next__())

Iterator with yield

FAILS
def func(n):
    for i in range(n):
        return i

WORKS
def func(n):
      for i in range(n):
         yield i

List vs Generator

# list generated and iterated through:
for v in [1 if x % 2 == 0 else 0 for x in range(10)]:
    print(v, end=" ")
print()

# subsequent values are generated one by one:
for v in (1 if x % 2 == 0 else 0 for x in range(10)):
    print(v, end=" ")
print()

File streams

read

write

update

File streams open, close, std

open()	open stream
close()	close stream
standard streams with 'import sys'	sys.stdin
	sys.stdout
	sys.stderr

File streams continued

'r'	read mode
'w'	write mode
'a'	append mode
'r+'	read and update mode
'w+'	write and update mode
'rt' / 'rb'	read text / binary
'wt' / 'wb'	write text / binary
'at' / 'ab'	append text / binary
'r+t' / 'r+b'	read and update text/binary
'w+t' / 'w+b'	write and update text/binary

OS Moudle

os.uname()	doesn't work with Windows
os.name()	works with Windows
os.listdir()	print directories
os.mkdir()	create directory
os.makedirs()	create multiple directories
os.chdir()	change directory
os.getcwd()	show current directory
os.rmdir()	delete directory
os.removedirs()	removes directories recursively

Datetime Module - Class Date

from datetime import date

v_today = date.today()

print(v_today.year)
print(v_today.month)
print(v_today.day)
print(v_today.today)

###

from datetime import date

d = date(2019, 11, 4)
print(d.weekday())
print(d.isoweekday())

Datetime Module - Class Time

from datetime import time

t = time(14, 53, 20, 1)

print("Time:", t)
print("Hour:", t.hour)
print("Minute:", t.minute)
print("Second:", t.second)
print("Microsecond:", t.microsecond)

Date and time operations

from datetime import date
from datetime import datetime

d1 = date(2020, 11, 4)
d2 = date(2019, 11, 4)

print(d1 - d2)

dt1 = datetime(2020, 11, 4, 0, 0, 0)
dt2 = datetime(2019, 11, 4, 14, 53, 0)

print(dt1 - dt2)

Calendar Module

import calendar

print(calendar.calendar(2023))
calendar.prcal(2023)

Calender for a month

import calendar
print(calendar.month(2020, 11))

Calendar Objects

import calendar  

c = calendar.Calendar(calendar.SUNDAY)

for weekday in c.iterweekdays():
    print(weekday, end=" ")

Calender Create Classes

calender.Calender	provides methods for calender data formatting
calendar.TextCalendar	create text calendars
calendar.HTMLCalendar	create HTML calendars
calendar.LocalTextCalendar	subclass (see above) uses local parameter
calendar.LocalHTMLCalendar	subclass (see above) uses local parameter

Calender set first week day

import calendar

calendar.setfirstweekday(calendar.SUNDAY)
calendar.prmonth(2020, 12)

PIP

pip --version	show pip version (pip version 2)
pip3 --version	show pip version (pip version 3)
pip help	show pip commands
pip help operation	show info about a specific operation
pip show package_name	show info about installed package
pip search string	search for a package
pip install package	package installation

String Operations

ord()	ordinal, code point
chr()	character
possible operations	indexing, iterating, slicing, 'in' and 'not' operators
impossible operations (immutable)	append, del, insert
max(), min()	uses ASCII value
additional operations	index(), list(), count()

String Methods

capitalize()	stRiNGdiNg -> stRiNGdiNg
endswith(suffix[, start[, end]])	'stringding'.endswith('ding') return True
find(sub[, start[, end]])	'stringding'.find('in') return 3 (index #)
isalum()	'string10' -> True, 'string_10' -> False
isalpha()	'string' -> True, 'string10' -> False
isdigit()	'10' -> True, 'string10' -> False
islower()	'stringding' -> True, 'strinGDing' -> False
isspace()	' \n ' -> True, ' ' -> True, 'string ding' -> False
isupper()	'string' -> False, 'stRINg' -> False, 'STRING' -> True
join()	",".join(['li', 'st', 'joined'] -> 'li,st,joined'
lower()	'stRinGDing' ->'stringding'
lstrip(str)	'stringding'.lstrip('str') -> 'ingding'
rstrip(str)	'stringding'.rstrip('ding') -> 'str'
replace(old, new[, count])	'stringding'.lstrip('str') -> 'strAngdAng'
rfind(sub[, start[, end]])	'stringding'.rfind('n') -> 8, ('n', 5) -> 8, ('n', 10) -> -1 (failure)
split(str)	'stringding'.split('i') -> ['str', 'ngd', 'ng']
startswith(str)	'stringding'.startswith('str') -> True, 'stringding'.startswith('ring') -> False
strip() remove leading, trailing whitespaces	' stringding ' -> 'stringding'
swapcase()	'strinGDiNg' -> 'STRINgdInG'
title()	'this Is a title' -> 'This Is A Title'
upper()	'strinGDiNg' -> 'STRINGDING'

String Comparison

Compare	==, !=, <, >, <=, >=
string == number	False
string != umber	True
string >= number	Exception

OOP - Method Invocation

class Sample:
    def other(self):
        print("other")

    def method(self):
        print("method")
        self.other()


obj = Sample()
obj.method()

OOP - Constructor

class Sample:
def __init__(self, value = None):
self.var = value

obj_1 = Sample("object")
obj_2 = Sample()

print(obj_1.var)
print(obj_2.var)

OOP - Hiding

class Sample:
def visible(self):
print("visible")

def __hidden(self):
print("hidden")

obj = Sample()
obj.visible()

try:
obj.__hidden()
except:
print("failed")

obj._Sample__hidden()

Exception continued

try:
   this is what we want
except:
   this is what we do with errors
else:
   we do this when no exception has been raised and our "try" was successful
final:
   no matter of what the outcome is we do that

Exceptions are classes

try:
    raise Exception
except Exception as e:
    print(e, e.__str__(), e.args)

Lambda

lambda parameter: expression	lambda x: x * 2
	lambda x, y: x * y
	lambda x, y, z: (x * y) / z

map() function

map(arg1, arg2)	list = list(map(lambda x: x * 2, sourcelist))
arg1	a function what to do
arg2	iterable object (list, tuple, generator, ...)

filter() function

filter items based on a given statement
filter(arg1, arg2)	list = list(filter(lambda x: x > 2, sourcelist))
arg1	function to what to filter
arg2	iterable object (list, tuple, generator, ...)

Conditional Expression

print(True if 0 ≥ 0 else False)

Work with files

read(1)	read chars -> 1 byte chunks
read()	read chars all at once
readline(10)	read lines -> 10 byte chunks
readline()	read full line
readlines(10)	read all lines -> 10 byte size chunks
readlines()	read all lines
write(arg1)	write to a file

Bytearray

data = bytearray(10)	creates a bytearray filled with 0's
	are mutable, len(), index()
	only integers, only 0 to 255

Bytearray - write to binary file

from os import strerror

data = bytearray(10)

for i in range(len(data)):
    data[i] = 10 + i

try:
    bf = open('file.bin', 'wb')
    bf.write(data)
    bf.close()
except IOError as e:
    print("I/O error occurred:", strerror(e.errno))

Bytearray - read from binary file

from os import strerror

data = bytearray(10)

try:
    binary_file = open('file.bin', 'rb')
    binary_file.readinto(data) # file.read(data) would also work
    binary_file.close()

    for b in data:
        print(hex(b), end=' ')
except IOError as e:
    print("I/O error occurred:", strerror(e.errno))

Time Module

import time

timestamp = 1572879180
print(time.ctime(timestamp))
print(time.gmtime(timestamp))
print(time.localtime(timestamp))

print(time.ctime())

timestamp()

from datetime import datetime

dt = datetime(2020, 10, 4, 14, 55)
print("Timestamp:", dt.timestamp())

strftime()

from datetime import time
from datetime import datetime

t = time(14, 53)
print(t.strftime("%H:%M:%S"))

dt = datetime(2020, 11, 4, 14, 53)
print(dt.strftime("%y/%B/%d %H:%M:%S"))

stftime() in Time Module

import time

timestamp = 1572879180
st = time.gmtime(timestamp)

print(time.strftime("%Y/%m/%d %H:%M:%S", st))
print(time.strftime("%Y/%m/%d %H:%M:%S"))

timedelta()

from datetime import timedelta
 
delta = timedelta(weeks=2, days=2, hours=3)
print(delta)
print("Days:", delta.days)
print("Seconds:", delta.seconds)
print("Microseconds:", delta.microseconds)

###

from datetime import timedelta
from datetime import date
from datetime import datetime

delta = timedelta(weeks=2, days=2, hours=2)
print(delta)

delta2 = delta * 2
print(delta2)

d = date(2019, 10, 4) + delta2
print(d)

dt = datetime(2019, 10, 4, 14, 53) + delta2
print(dt)

Calender Iterators

itermonthdates()	returns days of the week as int
itermonthdates2()	return tuple day of the month int and week day int
itermonthdays3()	return days as tuple year int, month int, day of month int
itermonthdays4()	return days as tuple with year int, month int day of month int, day of week int

Leap Year

isleap(<year>)	Check is year specified is leap year
leapdays(<year1, year2>)	returns number of lead years in specified range

Calender weekday()

import calendar
print(calendar.weekday(2020, 12, 24))