@ -101,12 +101,12 @@ Set
```
```python
< set > = < set > .union(< collection > ) # Or: < set > | < set >
< set > = < set > .intersection(< collection > ) # Or: < set > & < set >
< set > = < set > .difference(< collection > ) # Or: < set > - < set >
< set > = < set > .symmetric_difference(< collection > ) # Or: < set > ^ < set >
< bool > = < set > .issubset(< collection > ) # Or: < set > < < set >
< bool > = < set > .issuperset(< collection > ) # Or: < set > > < set >
< set > = < set > .union(< coll. > ) # Or: < set > | < set >
< set > = < set > .intersection(< coll. > ) # Or: < set > & < set >
< set > = < set > .difference(< coll. > ) # Or: < set > - < set >
< set > = < set > .symmetric_difference(< coll. > ) # Or: < set > ^ < set >
< bool > = < set > .issubset(< coll. > ) # Or: < set > < = < set >
< bool > = < set > .issuperset(< coll. > ) # Or: < set > >= < set >
```
### Frozenset
@ -158,6 +158,11 @@ Point(x=1, y=2)
Iterator
--------
```python
< iter > = iter(< collection > )
< iter > = iter(< function > , to_exclusive)
```
#### Skips first element:
```python
next(< iter > )
@ -184,10 +189,10 @@ Generator
**Convenient way to implement the iterator protocol.**
```python
def step(start, step):
def step(start, step_size ):
while True:
yield start
start += step
start += step_size
```
```python
@ -205,8 +210,11 @@ Type
```python
from numbers import Number, Integral, Real, Rational, Complex
is_number = isinstance(< el > , Number)
is_function = callable(< el > )
< bool > = isinstance(< el > , Number)
```
```python
< bool > = callable(< el > )
```
@ -219,7 +227,7 @@ String
```python
< list > = < str > .split() # Splits on any whitespace character.
< list > = < str > .split(sep=None, maxsplit=-1) # Splits on 'sep' at most 'maxsplit' times.
< list > = < str > .split(sep=None, maxsplit=-1) # Splits on 'sep' str at most 'maxsplit' times.
< str > = < str > .join(< list > ) # Joins elements using string as separator.
```
@ -265,12 +273,12 @@ Regex
-----
```python
import re
< str > = re.sub(< regex > , new, text, count=0) # Substitutes all occurrences.
< list > = re.findall(< regex > , text)
< list > = re.split(< regex > , text, maxsplit=0) # Use brackets in regex to keep the matches.
< Match > = re.search(< regex > , text) # Searches for first occurrence of pattern.
< Match > = re.match(< regex > , text) # Searches only at the beginning of the text.
< Match_iter > = re.finditer(< regex > , text) # Searches for all occurrences of pattern.
< str > = re.sub(< regex > , new, text, count=0) # Substitutes all occurrences.
< list > = re.findall(< regex > , text) # Returns all occurrences.
< list > = re.split(< regex > , text, maxsplit=0) # Use brackets in regex to keep the matches.
< Match > = re.search(< regex > , text) # Searches for first occurrence of pattern.
< Match > = re.match(< regex > , text) # Searches only at the beginning of the text.
< Matches > = re.finditer(< regex > , text) # Searches for all occurrences of pattern.
```
* **Parameter `'flags=re.IGNORECASE'` can be used with all functions.**
@ -323,7 +331,7 @@ Format
### String Options
**"!r" uses object's repr() method, instead of format(), to get a string:**
```python
{'abcde'!r} # "'abcde'"
{'abcde'!r:< 10 } # " ' abcde ' "
```
```python
@ -338,11 +346,11 @@ Format
```
```python
{123456:10,} # ' 123,456'
{123456:10_} # ' 123_456'
{123456:+10} # ' +123456'
{ 123456:10,} # ' 123,456'
{ 123456:10_} # ' 123_456'
{ 123456:+10} # ' +123456'
{-123456:=10} # '- 123456'
{123456: } # ' 123456'
{ 123456: } # ' 123456'
{-123456: } # '-123456'
```
@ -368,9 +376,9 @@ Numbers
-------
### Basic Functions
```python
pow(x, y) # Or: x ** y
abs(< num > )
round(< num > [, ndigits])
< num > = pow(< num > , < num > ) # Or: < num > ** < num >
< real > = < num > )
< real > = < real > [, ndigits])
```
### Constants
@ -386,9 +394,7 @@ from math import cos, acos, sin, asin, tan, atan, degrees, radians
### Logarithm
```python
from math import log, log10, log2
log(x [, base]) # Base e, if not specified.
log10(x) # Base 10.
log2(x) # Base 2.
< float > = log(< real > [, base]) # Base e, if not specified.
```
### Infinity, nan
@ -426,6 +432,7 @@ now.strftime('%Y%m%d%H%M%S') # '20180315002834'
Arguments
---------
**"*" is the splat operator, that takes a list as input, and expands it into actual positional arguments in the function call.**
```python
args = (1, 2)
kwargs = {'x': 3, 'y': 4, 'z': 5}
@ -473,7 +480,7 @@ lambda <argument_1>, <argument_2>: <return_value>
### Comprehension
```python
< list > = [i+1 for i in range(10)] # [1, 2, ..., 10]
< set > = {i for i in range(10) if i > 5} # {6, 7, ... , 9}
< set > = {i for i in range(10) if i > 5} # {6, 7, 8 , 9}
< dict > = {i: i*2 for i in range(10)} # {0: 0, 1: 2, ..., 9: 18}
< iter > = (i+5 for i in range(10)) # (5, 6, ..., 14)
```
@ -500,7 +507,8 @@ from functools import reduce
### Any, All
```python
< bool > = any(el[1] for el in < collection > )
< bool > = any(< collection > ) # False if empty.
< bool > = all(el[1] for el in < collection > ) # True if empty.
```
### If - Else
@ -587,10 +595,11 @@ Class
class < name > :
def __init__ (self, a):
self.a = a
def __repr__ (self):
class_name = type(self).__name__
return f'{class_name}({self.a:!r})'
def __str__ (self):
return str(self.a)
def __repr__ (self):
return str({'a': self.a}) # Or: return f'{self.__dict__}'
@classmethod
def get_class_name(cls):
@ -640,11 +649,11 @@ class <enum_name>(Enum):
```
```python
< member > = < enum > .< member_name >
< member > = < enum > ['< member_name > ']
< member > = < enum > (< value > )
< name > < member > .name
< value > < member > .value
< member > = < enum > .< member_name >
< member > = < enum > ['< member_name > ']
< member > = < enum > (< value > )
name = < member > .name
value = < member > .value
```
```python
@ -725,6 +734,8 @@ b'.\n..\nfile1.txt\nfile2.txt\n'
```
### Input
**Reads a line from user input or pipe if present. The trailing newline gets stripped.**
```python
filename = input('Enter a file name: ')
```
@ -740,9 +751,10 @@ while True:
### Recursion Limit
```python
>>> import sys
>>> sys.getrecursionlimit()
1000
>>> sys.setrecursionlimit(10 000)
>>> sys.setrecursionlimit(5 000)
```
JSON
@ -783,6 +795,8 @@ SQLite
```python
import sqlite3
db = sqlite3.connect(< filename > )
...
db.close()
```
### Read
@ -791,7 +805,6 @@ cursor = db.execute(<query>)
if cursor:
< tuple > = cursor.fetchone() # First row.
< list > = cursor.fetchall() # Remaining rows.
db.close()
```
### Write
@ -845,21 +858,27 @@ KeyboardInterrupt
Bytes
-----
**Bytes objects are immutable sequences of single bytes.**
**Bytes object is immutable sequence of single bytes. Mutable version is called bytearray. **
```python
< int > = < bytes > [< index > ]
< bytes > = < bytes > [< slice > ]
< bytes > = b''.join(< coll_of_bytes > )
```
### Encode
```python
< Bytes > = b'< str > '
< Bytes > = < str > .encode(encoding='utf-8')
< Bytes > = < int > .to_bytes(< length > , byteorder='big|little', signed=False)
< B ytes> = bytes.fromhex(< hex > )
< b ytes> = b'< str > '
< b ytes> = < str > .encode(encoding='utf-8')
< b ytes> = < int > .to_bytes(< length > , byteorder='big|little', signed=False)
< b ytes> = bytes.fromhex(< hex > )
```
### Decode
```python
< str > = < B ytes> .decode('utf-8')
< int > = int.from_bytes(< B ytes> , byteorder='big|little', signed=False)
< hex > = < B ytes> .hex()
< str > = < b ytes> .decode('utf-8')
< int > = int.from_bytes(< b ytes> , byteorder='big|little', signed=False)
< hex > = < b ytes> .hex()
```
### Read Bytes from File
@ -871,50 +890,53 @@ def read_bytes(filename):
### Write Bytes to File
```python
def write_bytes(filename, bytes):
def write_bytes(filename, bytes_obj ):
with open(filename, 'wb') as file:
file.write(bytes)
```
```python
< Bytes > = b''.join(< list_of_Bytes > )
file.write(bytes_obj)
```
Struct
------
**This module performs conversions between Python values and C struct represented as Python Bytes object.**
**This module performs conversions between Python values and C struct represented as Python bytes object. By default machine’s native sizes and byte order are used.**
```python
from struct import pack, unpack
< B ytes> = pack('< format > ', < value_1 > [, < value_2 > , ...])
< tuple > = unpack('< format > ', < B ytes> )
from struct import pack, unpack, calcsize
< b ytes> = pack('< format > ', < value_1 > [, < value_2 > , ...])
< tuple > = unpack('< format > ', < b ytes> )
```
### Example
```python
>>> pack('hhl', 1, 2, 3)
>>> pack('> hhl', 1, 2, 3)
b'\x00\x01\x00\x02\x00\x00\x00\x03'
>>> unpack('hhl', b'\x00\x01\x00\x02\x00\x00\x00\x03')
>>> unpack('> hhl', b'\x00\x01\x00\x02\x00\x00\x00\x03')
(1, 2, 3)
>>> calcsize('hhl')
>>> calcsize('> hhl')
8
```
### Format
**Use capital leters for unsigned type.**
**For standard sizes start format string with:**
* `'='` - native byte order
* `'<'` - little-endian
* `'>'` - big-endian
**Use capital leter for unsigned type. Standard size in brackets.**
* `'x'` - pad byte
* `'c'` - char
* `'h'` - short
* `'i'` - int
* `'l'` - long
* `'q'` - long long
* `'f'` - float
* `'d'` - double
* `'c'` - char (1)
* `'h'` - short (2)
* `'i'` - int (4)
* `'l'` - long (4)
* `'q'` - long long (8)
* `'f'` - float (4)
* `'d'` - double (8)
Hashlib
-------
```python
>>> import hashlib
>>> hashlib.md5(< str > .encode()).hexdigest()
'33d0eba106da4d3ebca17fcd3f4c3d77'
```
@ -936,7 +958,7 @@ thread.join()
### Lock
```python
lock = Rl ock()
lock = RL ock()
lock.acquire()
...
lock.release()
@ -945,7 +967,7 @@ lock.release()
Itertools
---------
**Every function returns an iterator and can accept any collection and/or iterator. If you want to print the iterator, you need to pass it to the list() function. **
**Every function returns an iterator and can accept any collection and/or iterator. If you want to print the iterator, you need to pass it to the list() function! **
```python
from itertools import *
@ -1022,9 +1044,9 @@ Introspection and Metaprograming
### Variables
```python
< list > = dir() # I n-scope variables.
< dict > = locals() # Local variables .
< dict > = globals() # G lobal variables.
< list > = dir() # Names of i n-scope variables.
< dict > = locals() # Dict of local variables, same as vars() .
< dict > = globals() # Dict of g lobal variables.
```
### Attributes
@ -1050,11 +1072,11 @@ False
```
### Parameters
#### Getting the number of parameters of a function:
```python
from inspect import signature
sig = signature(< function > )
no_of_params = len(sig.parameters)
param_names = list(sig.parameters.keys())
```
### Type
@ -1072,7 +1094,7 @@ type(<class_name>, <parents_tuple>, <attributes_dict>)
#### Class that creates class.
```python
def my_meta_class(name, parents, attrs):
attrs['a'] = 1
attrs['a'] = 'abcde'
return type(name, parents, attrs)
```
@ -1080,7 +1102,7 @@ def my_meta_class(name, parents, attrs):
```python
class MyMetaClass(type):
def __new__ (klass, name, parents, attrs):
attrs['a'] = 1
attrs['a'] = 'abcde'
return type.__new__(klass, name, parents, attrs)
```
@ -1089,7 +1111,7 @@ class MyMetaClass(type):
```python
class MyClass(metaclass=MyMetaClass):
def __init__ (self):
self.b = 2
self.b = 1 2345
```
@ -1121,7 +1143,7 @@ Eval
3
>>> literal_eval('[1, 2, 3]')
[1, 2, 3]
>>> ast.literal_eval('abs(- 1)')
>>> ast.literal_eval('abs(1)')
ValueError: malformed node or string
```
@ -1218,6 +1240,45 @@ reader(adder(printer())) # 100, 101, ..., 109
Libraries
=========
Argparse
--------
```python
import argparse
parser = argparse.ArgumentParser(description='calculate X to the power of Y')
group = parser.add_mutually_exclusive_group()
group.add_argument('-v', '--verbose', action='store_true')
group.add_argument('-q', '--quiet', action='store_true')
parser.add_argument('x', type=int, help='the base')
parser.add_argument('y', type=int, help='the exponent')
args = parser.parse_args()
answer = args.x ** args.y
if args.quiet:
print(answer)
elif args.verbose:
print('{args.x} to the power {args.y} equals {answer}')
else:
print('{args.x}^{args.y} == {answer}')
```
#### Usage:
```bash
$ python3 prog.py --help
usage: test2.py [-h] [-v | -q] x y
calculate X to the power of Y
positional arguments:
x the base
y the exponent
optional arguments:
-h, --help show this help message and exit
-v, --verbose
-q, --quiet
```
Plot
----
```python
@ -1235,10 +1296,10 @@ Progress Bar
# $ pip3 install tqdm
from tqdm import tqdm
from time import sleep
for i in tqdm(range(100)):
sleep(0.02)
for i in tqdm([1, 2, 3]):
sleep(0.2)
for i in tqdm(range(100)):
sleep(0.02)
```
@ -1348,7 +1409,7 @@ Scraping
>>> document = BeautifulSoup(page.text, 'html.parser')
>>> table = document.find('table', class_='infobox vevent')
>>> rows = table.find_all('tr')
>>> website = rows[11].find('a')['href']
>>> link = rows[11].find('a')['href']
'https://www.python.org/'
>>> latest_v = rows[6].find('div').text.split()[0]
'3.7.2'
@ -1396,7 +1457,7 @@ def odds_handler(sport):
home_odds, away_odds = get_odds(db, sport, team)
db.close()
response.headers['Content-Type'] = 'application/json'
response.headers['Content-Type'] = 'application/json'
response.headers['Cache-Control'] = 'no-cache'
return json.dumps([home_odds, away_odds])
```
@ -1456,6 +1517,7 @@ with PyCallGraph(output=graph):
NumPy
-----
**Array manipulation mini language. Can run up to 100 times faster than equivalent Python code.**
```python
# $ pip3 install numpy
import numpy as np
@ -1463,7 +1525,7 @@ import numpy as np
```python
< array > = np.array(< list > )
< array > = np.arange(from_inclusive, to_exclusive, step)
< array > = np.arange(from_inclusive, to_exclusive, step_size )
< array > = np.ones(< shape > )
< array > = np.random.randint(from_inclusive, to_exclusive, < shape > )
```
@ -1501,27 +1563,27 @@ right = [[0.1, 0.6, 0.8], [0.1, 0.6, 0.8], [0.1, 0.6, 0.8]] # Shape: (3, 3) <-
**For each point returns index of its nearest point: `[0.1, 0.6, 0.8] => [1, 2, 1]` .**
```python
>>> points = np.array([0.1, 0.6, 0.8])
array( [ 0.1, 0.6, 0.8])
[ 0.1, 0.6, 0.8]
>>> wrapped_points = points.reshape(3, 1)
array( [[ 0.1],
[ 0.6],
[ 0.8]])
[[ 0.1],
[ 0.6],
[ 0.8]]
>>> distances = wrapped_points - points
array( [[ 0. , -0.5, -0.7],
[ 0.5, 0. , -0.2],
[ 0.7, 0.2, 0. ]])
[[ 0. , -0.5, -0.7],
[ 0.5, 0. , -0.2],
[ 0.7, 0.2, 0. ]]
>>> distances = np.abs(distances)
array( [[ 0. , 0.5, 0.7],
[ 0.5, 0. , 0.2],
[ 0.7, 0.2, 0. ]])
[[ 0. , 0.5, 0.7],
[ 0.5, 0. , 0.2],
[ 0.7, 0.2, 0. ]]
>>> i = np.arange(3)
array( [0, 1, 2])
[0, 1, 2]
>>> distances[i, i] = np.inf
array( [[ inf, 0.5, 0.7],
[ 0.5, inf, 0.2],
[ 0.7, 0.2, inf]])
[[ inf, 0.5, 0.7],
[ 0.5, inf, 0.2],
[ 0.7, 0.2, inf]]
>>> distances.argmin(1)
array( [1, 2, 1])
[1, 2, 1]
```
Jure Šorn
6 years ago