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# Python Basics
## Usefull information
It is an interpreted language\
list(xrange()) == range() --> In python3 range is the xrange of python2 (it is not a list but a generator)\
The difference between a Tuple and a List is that the position of a value in a tuple gives it a meaning but the lists are just ordered values. Tuples have structures, lists have order
## Main operations
To raise a number you should do: 3**2 (it isn't 3^2)\
If you do 2/3 it returns 1 because you are dividing two ints. If you want decimals you should divide floats (2.0/3.0).\
i >= j\
i <= j\
i == j\
i != j\
a and b\
a or b\
not a\
float(a)\
int(a)\
str(d)\
ord("A") = 65\
chr(65) = 'A'\
hex(100) = '0x64'\
hex(100)\[2:] = '64'\
isinstance(1, int) = True\
"a b".split(" ") = \['a', 'b']\
" ".join(\['a', 'b']) = "a b"\
"abcdef".startswith("ab") = True\
"abcdef".contains("abc") = True\
"abc\n".strip() = "abc"\
"apbc".replace("p","") = "abc"\
dir(str) = List of all the availble methods\
help(str) = Definition of the class str\
"a".upper() = "A"\
"A".lower() = "a"\
"abc".capitalize() = "Abc"\
sum(\[1,2,3]) = 6\
sorted(\[1,43,5,3,21,4])
**Join chars**\
3 \* ’a’ = ‘aaa’\
‘a’ + ‘b’ = ‘ab’\
‘a’ + str(3) = ‘a3’\
\[1,2,3]+\[4,5]=\[1,2,3,4,5]
**Parts of a list**\
‘abc’\[0] = ‘a’\
'abc’\[-1] = ‘c’\
'abc’\[1:3] = ‘bc’ from \[1] to \[2]\
"qwertyuiop"\[:-1] = 'qwertyuio'
**Comments**\
\# One line comment\
"""\
Several lines comment\
Another one\
"""
**Loops**
```
if a:
#somethig
elif b:
#something
else:
#something
while(a):
#comething
for i in range(0,100):
#something from 0 to 99
for letter in "hola":
#something with letter in "hola"
```
## Tuples
t1 = (1,'2,'three')\
t2 = (5,6)\
t3 = t1 + t2 = (1, '2', 'three', 5, 6)\
(4,) = Singelton\
d = () empty tuple\
d += (4,) --> Adding into a tuple\
CANT! --> t1\[1] == 'New value'\
list(t2) = \[5,6] --> From tuple to list
## List (array)
d = \[] empty\
a = \[1,2,3]\
b = \[4,5]\
a + b = \[1,2,3,4,5]\
b.append(6) = \[4,5,6]\
tuple(a) = (1,2,3) --> From list to tuple
## Dictionary
d = {} empty\
monthNumbers={1:’Jan’, 2: ‘feb’,’feb’:2}—> monthNumbers ->{1:’Jan’, 2: ‘feb’,’feb’:2}\
monthNumbers\[1] = ‘Jan’\
monthNumbers\[‘feb’] = 2\
list(monthNumbers) = \[1,2,’feb’]\
monthNumbers.values() = \[‘Jan’,’feb’,2]\
keys = \[k for k in monthNumbers]\
a={'9':9}\
monthNumbers.update(a) = {'9':9, 1:’Jan’, 2: ‘feb’,’feb’:2}\
mN = monthNumbers.copy() #Independent copy\
monthNumbers.get('key',0) #Check if key exists, Return value of monthNumbers\["key"] or 0 if it does not exists
## Set
In the sets there are not repetitions\
myset = set(\['a', 'b']) = {'a', 'b'}\
myset.add('c') = {'a', 'b', 'c'}\
myset.add('a') = {'a', 'b', 'c'} #No repetitions\
myset.update(\[1,2,3]) = set(\['a', 1, 2, 'b', 'c', 3])\
myset.discard(10) #If present, remove it, if not, nothing\
myset.remove(10) #If present remove it, if not, rise exception\
myset2 = set(\[1, 2, 3, 4])\
myset.union(myset2) #Values it myset OR myset2\
myset.intersection(myset2) #Values in myset AND myset2\
myset.difference(myset2) #Values in myset but not in myset2\
myset.symmetric_difference(myset2) #Values that are not in myset AND myset2 (not in both)\
myset.pop() #Get the first element of the set and remove it\
myset.intersection_update(myset2) #myset = Elements in both myset and myset2\
myset.difference_update(myset2) #myset = Elements in myset but not in myset2\
myset.symmetric_difference_update(myset2) #myset = Elements that are not in both
## Classes
The method in \__It\_\_ will be the one used by sort in order to compare if an object of this class is bigger than other
```python
class Person(name):
def __init__(self,name):
self.name= name
self.lastName = name.split(‘ ‘)[-1]
self.birthday = None
def __It__(self, other):
if self.lastName == other.lastName:
return self.name < other.name
return self.lastName < other.lastName #Return True if the lastname is smaller
def setBirthday(self, month, day. year):
self.birthday = date tame.date(year,month,day)
def getAge(self):
return (date time.date.today() - self.birthday).days
class MITPerson(Person):
nextIdNum = 0 # Attribute of the Class
def __init__(self, name):
Person.__init__(self,name)
self.idNum = MITPerson.nextIdNum —> Accedemos al atributo de la clase
MITPerson.nextIdNum += 1 #Attribute of the class +1
def __it__(self, other):
return self.idNum < other.idNum
```
## map, zip, filter, lambda, sorted and one-liners
**Map** is like: \[f(x) for x in iterable] --> map(tutple,\[a,b]) = \[(1,2,3),(4,5)]\
m = map(lambda x: x % 3 == 0, \[1, 2, 3, 4, 5, 6, 7, 8, 9]) --> \[False, False, True, False, False, True, False, False, True]
**zip** stops when the shorter of foo or bar stops:
```
for f, b in zip(foo, bar):
print(f, b)
```
**Lambda** is used to define a function\
(lambda x,y: x+y)(5,3) = 8 --> Use lambda as simple **function**\
**sorted**(range(-5,6), key=lambda x: x** 2) = \[0, -1, 1, -2, 2, -3, 3, -4, 4, -5, 5] --> Use lambda to sort a list\
m = **filter**(lambda x: x % 3 == 0, \[1, 2, 3, 4, 5, 6, 7, 8, 9]) = \[3, 6, 9] --> Use lambda to filter\
**reduce** (lambda x,y: x\*y, \[1,2,3,4]) = 24
```
def make_adder(n):
return lambda x: x+n
plus3 = make_adder(3)
plus3(4) = 7 # 3 + 4 = 7
class Car:
crash = lambda self: print('Boom!')
my_car = Car(); my_car.crash() = 'Boom!'
```
mult1 = \[x for x in \[1, 2, 3, 4, 5, 6, 7, 8, 9] if x%3 == 0 ]
## Exceptions
```
def divide(x,y):
try:
result = x/y
except ZeroDivisionError, e:
print “division by zero!” + str(e)
except TypeError:
divide(int(x),int(y))
else:
print “result i”, result
finally
print “executing finally clause in any case”
```
## Assert()
If the condition is false the string will by printed in the screen
```
def avg(grades, weights):
assert not len(grades) == 0, 'no grades data'
assert len(grades) == 'wrong number grades'
```
## Generators, yield
A generator, instead of returning something, it "yields" something. When you access it, it will "return" the first value generated, then, you can access it again and it will return the next value generated. So, all the values are not generated at the same time and a lot of memory could be saved using this instead of a list with all the values.
```
def myGen(n):
yield n
yield n + 1
```
g = myGen(6) --> 6\
next(g) --> 7\
next(g) --> Error
## Regular Expresions
import re\
re.search("\w","hola").group() = "h"\
re.findall("\w","hola") = \['h', 'o', 'l', 'a']\
re.findall("\w+(la)","hola caracola") = \['la', 'la']
**Special meanings:**\
. --> Everything\
\w --> \[a-zA-Z0-9\_]\
\d --> Number\
\s --> WhiteSpace char\[ \n\r\t\f]\
\S --> Non-whitespace char\
^ --> Starts with\
$ --> Ends with\
\+ --> One or more\
\* --> 0 or more\
? --> 0 or 1 occurrences
**Options:**\
re.search(pat,str,re.IGNORECASE)\
IGNORECASE\
DOTALL --> Allow dot to match newline\
MULTILINE --> Allow ^ and $ to match in different lines
re.findall("<.\*>", "\foo\and\so on\") = \['\foo\and\so on\']\
re.findall("<.\*?>", "\foo\and\so on\") = \['\', '\', '\', '\']
IterTools\
**product**\
from **itertools** import product --> Generates combinations between 1 or more lists, perhaps repeating values, cartesian product (distributive property)\
print list(**product**(\[1,2,3],\[3,4])) = \[(1, 3), (1, 4), (2, 3), (2, 4), (3, 3), (3, 4)]\
print list(**product**(\[1,2,3],repeat = 2)) = \[(1, 1), (1, 2), (1, 3), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (3, 3)]
**permutations**\
from **itertools** import **permutations** --> Generates combinations of all characters in every position\
print list(permutations(\['1','2','3'])) = \[('1', '2', '3'), ('1', '3', '2'), ('2', '1', '3'),... Every posible combination\
print(list(permutations('123',2))) = \[('1', '2'), ('1', '3'), ('2', '1'), ('2', '3'), ('3', '1'), ('3', '2')] Every posible combination of lenght 2
**combinations**\
from itertools import **combinations** --> Generates all possible combinations without repeating characters (if "ab" existing, doesn't generate "ba")\
print(list(**combinations**('123',2))) --> \[('1', '2'), ('1', '3'), ('2', '3')]
**combinations_with_replacement**\
from itertools import **combinations_with_replacement** --> Generates all possible combinations from the char onwards(for example, the 3rd is mixed from the 3rd onwards but not with the 2nd o first)\
print(list(**combinations_with_replacement**('1133',2))) = \[('1', '1'), ('1', '1'), ('1', '3'), ('1', '3'), ('1', '1'), ('1', '3'), ('1', '3'), ('3', '3'), ('3', '3'), ('3', '3')]
## Decorators
Decorator that size the time that a function needs to be executed (from [here](https://towardsdatascience.com/decorating-functions-in-python-619cbbe82c74)):
```python
from functools import wraps
import time
def timeme(func):
@wraps(func)
def wrapper(*args, **kwargs):
print("Let's call our decorated function")
start = time.time()
result = func(*args, **kwargs)
print('Execution time: {} seconds'.format(time.time() - start))
return result
return wrapper
@timeme
def decorated_func():
print("Decorated func!")
```
If you run it, you will see something like the following:
```
Let's call our decorated function
Decorated func!
Execution time: 4.792213439941406e-05 seconds
```
Support HackTricks and get benefits!
Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
**Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
**Share your hacking tricks submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**