diff --git a/README.md b/README.md
index 90631ba..5a08795 100644
--- a/README.md
+++ b/README.md
@@ -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> = abs(<num>)
+<real> = round(<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(10000)
+>>> sys.setrecursionlimit(5000)
```
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)
-<Bytes> = bytes.fromhex(<hex>)
+<bytes> = b'<str>'
+<bytes> = <str>.encode(encoding='utf-8')
+<bytes> = <int>.to_bytes(<length>, byteorder='big|little', signed=False)
+<bytes> = bytes.fromhex(<hex>)
```
### Decode
```python
-<str> = <Bytes>.decode('utf-8')
-<int> = int.from_bytes(<Bytes>, byteorder='big|little', signed=False)
-<hex> = <Bytes>.hex()
+<str> = <bytes>.decode('utf-8')
+<int> = int.from_bytes(<bytes>, byteorder='big|little', signed=False)
+<hex> = <bytes>.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
-<Bytes> = pack('<format>', <value_1> [, <value_2>, ...])
-<tuple> = unpack('<format>', <Bytes>)
+from struct import pack, unpack, calcsize
+<bytes> = pack('<format>', <value_1> [, <value_2>, ...])
+<tuple> = unpack('<format>', <bytes>)
```
### 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 = Rlock()
+lock = RLock()
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() # In-scope variables.
-<dict> = locals() # Local variables.
-<dict> = globals() # Global variables.
+<list> = dir() # Names of in-scope variables.
+<dict> = locals() # Dict of local variables, same as vars().
+<dict> = globals() # Dict of global 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 = 12345
```
@@ -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]
```