From 9c81a492b576d6074f6e052e85ea7b71916d9ae5 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Jure=20=C5=A0orn?= Date: Sat, 22 Jul 2023 17:06:00 +0200 Subject: [PATCH] Class, Duck types, Open, Memory view, Operator, Metaprogramming, Web, Profile --- README.md | 18 +++++++++--------- index.html | 22 +++++++++++----------- 2 files changed, 20 insertions(+), 20 deletions(-) diff --git a/README.md b/README.md index de2cc7a..85ab581 100644 --- a/README.md +++ b/README.md @@ -1068,7 +1068,7 @@ from dataclasses import make_dataclass #### Rest of type annotations (CPython interpreter ignores them all): ```python -import typing as tp, collections.abc as abc +import collections.abc as abc, typing as tp : list/set/abc.Iterable/abc.Sequence/tp.Optional[] [= ] : dict/tuple/tp.Union[, ...] [= ] def func(: [= ]) -> : ... @@ -1252,7 +1252,7 @@ True ### Collection * **Only required methods are iter() and len(). Len() should return the number of items.** * **This cheatsheet actually means `''` when it uses `''`.** -* **I chose not to use the name 'iterable' because it sounds scarier and more vague than 'collection'. The only drawback of this decision is that a reader could think a certain function doesn't accept iterators when it does, since iterators are the only built-in objects that are iterable but are not collections.** +* **I chose not to use the name 'iterable' because it sounds scarier and more vague than 'collection'. The only drawback of this decision is that the reader could think a certain function doesn't accept iterators when it does, since iterators are the only built-in objects that are iterable but are not collections.** ```python class MyCollection: def __init__(self, a): @@ -1606,7 +1606,7 @@ Open .writelines() # Writes a coll. of strings or bytes objects. .flush() # Flushes write buffer. Runs every 4096/8192 B. ``` -* **Methods do not add or strip trailing newlines, even writelines().** +* **Methods do not add or strip trailing newlines, not even writelines().** ### Read Text from File ```python @@ -2045,7 +2045,7 @@ from array import array Memory View ----------- -* **A sequence object that points to the memory of another object.** +* **A sequence object that points to the memory of another bytes-like object.** * **Each element can reference a single or multiple consecutive bytes, depending on format.** * **Order and number of elements can be changed with slicing.** * **Casting only works between char and other types and uses system's sizes.** @@ -2177,7 +2177,7 @@ product_of_elems = functools.reduce(op.mul, ) union_of_sets = functools.reduce(op.or_, ) first_element = op.methodcaller('pop', 0)() ``` -* **Binary operators require objects to have and(), or(), xor() and invert() special methods, unlike logical operators that work on all types of objects.** +* **Bitwise operators require objects to have and(), or(), xor() and invert() special methods, unlike logical operators that work on all types of objects.** * **Also: `' = &|^ '` and `' = &|^ '`.** @@ -2250,7 +2250,7 @@ class MyMetaClass(type): * **The only difference between the examples above is that my\_meta\_class() returns a class of type type, while MyMetaClass() returns a class of type MyMetaClass.** ### Metaclass Attribute -**Right before a class is created it checks if it has the 'metaclass' attribute defined. If not, it recursively checks if any of his parents has it defined and eventually comes to type().** +**Right before a class is created it checks if it has the 'metaclass' attribute defined. If not, it recursively checks if any of its parents has it defined and eventually comes to type().** ```python class MyClass(metaclass=MyMetaClass): @@ -2535,7 +2535,7 @@ from flask import Flask, send_from_directory, render_template_string, request ```python app = Flask(__name__) -app.run(host=None, debug=None) +app.run(host=None, port=None, debug=None) ``` * **Starts the app at `'http://localhost:5000'`. Use `'host="0.0.0.0"'` to run externally.** * **Install a WSGI server like [Waitress](https://flask.palletsprojects.com/en/latest/deploying/waitress/) and a HTTP server such as [Nginx](https://flask.palletsprojects.com/en/latest/deploying/nginx/) for better security.** @@ -2599,11 +2599,11 @@ duration_in_seconds = perf_counter() - start_time ### Profiling by Line ```text $ pip3 install line_profiler -$ echo "@profile +$ echo '@profile def main(): a = list(range(10000)) b = set(range(10000)) -main()" > test.py +main()' > test.py $ kernprof -lv test.py Line # Hits Time Per Hit % Time Line Contents ======================================================= diff --git a/index.html b/index.html index 0f35e4a..c425e23 100644 --- a/index.html +++ b/index.html @@ -54,7 +54,7 @@
- +
@@ -903,7 +903,7 @@ Z = dataclasses.make_dataclass('Z', ['<class_name>', <coll_of_tuples>) <tuple> = ('<attr_name>', <type> [, <default_value>]) -

Rest of type annotations (CPython interpreter ignores them all):

import typing as tp, collections.abc as abc
+
Rest of type annotations (CPython interpreter ignores them all):
import collections.abc as abc, typing as tp
 <var_name>: list/set/abc.Iterable/abc.Sequence/tp.Optional[<type>] [= <obj>]
 <var_name>: dict/tuple/tp.Union[<type>, ...] [= <obj>]
 def func(<arg_name>: <type> [= <obj>]) -> <type>: ...
@@ -1067,7 +1067,7 @@ Hello World!
 
Collection
    
 
  • Only required methods are iter() and len(). Len() should return the number of items.
    • 
 
  • This cheatsheet actually means '<iterable>' when it uses '<collection>'.
    • 
-
  • I chose not to use the name 'iterable' because it sounds scarier and more vague than 'collection'. The only drawback of this decision is that a reader could think a certain function doesn't accept iterators when it does, since iterators are the only built-in objects that are iterable but are not collections.
    • 
+
  • I chose not to use the name 'iterable' because it sounds scarier and more vague than 'collection'. The only drawback of this decision is that the reader could think a certain function doesn't accept iterators when it does, since iterators are the only built-in objects that are iterable but are not collections.
    • 
 
class MyCollection:
     def __init__(self, a):
         self.a = a
@@ -1371,7 +1371,7 @@ value = args.<name>
 <file>.flush()                      # Flushes write buffer. Runs every 4096/8192 B.
 

 
    
-
  • Methods do not add or strip trailing newlines, even writelines().
    • 
+
  • Methods do not add or strip trailing newlines, not even writelines().
    • 
 

 
Read Text from File
def read_file(filename):
     with open(filename, encoding='utf-8') as file:
@@ -1697,7 +1697,7 @@ CompletedProcess(args=['bc', #Memory View
    
-
  • A sequence object that points to the memory of another object.
    • 
+
  • A sequence object that points to the memory of another bytes-like object.
    • 
 
  • Each element can reference a single or multiple consecutive bytes, depending on format.
    • 
 
  • Order and number of elements can be changed with slicing.
    • 
 
  • Casting only works between char and other types and uses system's sizes.
    • 
@@ -1801,7 +1801,7 @@ union_of_sets    = functools.reduce(op.or_, <coll_of_sets>)
 first_element    = op.methodcaller('pop', 0)(<list>)
 

 
    
-
  • Binary operators require objects to have and(), or(), xor() and invert() special methods, unlike logical operators that work on all types of objects.
    • 
+
  • Bitwise operators require objects to have and(), or(), xor() and invert() special methods, unlike logical operators that work on all types of objects.
    • 
 
  • Also: '<bool> = <bool> &|^ <bool>' and '<int> = <bool> &|^ <int>'.
    • 
 

 
#Introspection
Inspecting code at runtime.
Variables
<list> = dir()                             # Names of local variables (incl. functions).
@@ -1852,7 +1852,7 @@ delattr(<object>, '<attr_name>')
 
  • Like in our case, new() can also be called directly, usually from a new() method of a child class (def __new__(cls): return super().__new__(cls)).
    • 
 
  • The only difference between the examples above is that my_meta_class() returns a class of type type, while MyMetaClass() returns a class of type MyMetaClass.
    • 
 
-
    Metaclass Attribute
    Right before a class is created it checks if it has the 'metaclass' attribute defined. If not, it recursively checks if any of his parents has it defined and eventually comes to type().
    class MyClass(metaclass=MyMetaClass):
+
    Metaclass Attribute
    Right before a class is created it checks if it has the 'metaclass' attribute defined. If not, it recursively checks if any of its parents has it defined and eventually comes to type().
    class MyClass(metaclass=MyMetaClass):
     b = 12345
 
    
 
@@ -2080,7 +2080,7 @@ WIKI_URL = 'https://en.wikipedia.org/wiki/Python_(prog
 
 
 
    app = Flask(__name__)
-app.run(host=None, debug=None)
+app.run(host=None, port=None, debug=None)
 
    
 
      
 
    • Starts the app at 'http://localhost:5000'. Use 'host="0.0.0.0"' to run externally.
      • 
@@ -2130,11 +2130,11 @@ duration_in_seconds = perf_counter() - start_time
 
    
 
 
    Profiling by Line
    $ pip3 install line_profiler
-$ echo "@profile
+$ echo '@profile
 def main():
     a = list(range(10000))
     b = set(range(10000))
-main()" > test.py
+main()' > test.py
 $ kernprof -lv test.py
 Line #   Hits     Time  Per Hit   % Time  Line Contents
 =======================================================
@@ -2933,7 +2933,7 @@ $ pyinstaller script.py --add-data '<path>:.'