diff --git a/README.md b/README.md index 1461783..0030519 100644 --- a/README.md +++ b/README.md @@ -975,15 +975,15 @@ class MyClass: def get_class_name(cls): return cls.__name__ ``` -* **Return value of str() should be readable and of repr() unambiguous.** -* **If only repr() is defined, it will also be used for str().** -* **Methods decorated with `'@staticmethod'` do not receive 'self' nor 'cls' as their first arg.** ```python >>> obj = MyClass(1) >>> obj.a, str(obj), repr(obj) (1, '1', 'MyClass(1)') ``` +* **Return value of str() should be readable and of repr() unambiguous.** +* **If only repr() is defined, it will also be used for str().** +* **Methods decorated with `'@staticmethod'` do not receive 'self' nor 'cls' as their first argument.** #### Expressions that call the str() method: ```python @@ -1769,22 +1769,22 @@ JSON ```python import json - = json.dumps() # Converts object to JSON string. - = json.loads() # Converts JSON string to object. + = json.dumps() # Converts collection to JSON string. + = json.loads() # Converts JSON string to collection. ``` -### Read Object from JSON File +### Read Collection from JSON File ```python def read_json_file(filename): with open(filename, encoding='utf-8') as file: return json.load(file) ``` -### Write Object to JSON File +### Write Collection to JSON File ```python -def write_to_json_file(filename, an_object): +def write_to_json_file(filename, list_or_dict): with open(filename, 'w', encoding='utf-8') as file: - json.dump(an_object, file, ensure_ascii=False, indent=2) + json.dump(list_or_dict, file, ensure_ascii=False, indent=2) ``` @@ -1884,41 +1884,41 @@ def write_to_csv_file(filename, rows, mode='w', **csv_params): SQLite ------ -**A server-less database engine that stores each database into a separate file.** +**A server-less database engine that stores each database into its own file.** ```python import sqlite3 - = sqlite3.connect() # Opens existing or new file. Also ':memory:'. -.close() # Closes connection. Discards uncommitted data. + = sqlite3.connect() # Opens existing or new file. Also ':memory:'. +.close() # Closes connection. Discards uncommitted data. ``` ### Read ```python - = .execute('') # Can raise a subclass of sqlite3.Error. - = .fetchone() # Returns next row. Also next(). - = .fetchall() # Returns remaining rows. Also list(). + = .execute('') # Can raise a subclass of sqlite3.Error. + = .fetchone() # Returns next row. Also next(). + = .fetchall() # Returns remaining rows. Also list(). ``` ### Write ```python -.execute('') # Can raise a subclass of sqlite3.Error. -.commit() # Saves all changes since the last commit. -.rollback() # Discards all changes since the last commit. +.execute('') # Can raise a subclass of sqlite3.Error. +.commit() # Saves all changes since the last commit. +.rollback() # Discards all changes since the last commit. ``` #### Or: ```python -with : # Exits the block with commit() or rollback(), - .execute('') # depending on whether any exception occurred. +with : # Exits the block with commit() or rollback(), + .execute('') # depending on whether any exception occurred. ``` ### Placeholders ```python -.execute('', ) # Replaces '?'s in query with values. -.execute('', ) # Replaces ':'s with values. -.executemany('', ) # Runs execute() multiple times. +.execute('', ) # Replaces '?'s in query with values. +.execute('', ) # Replaces ':'s with values. +.executemany('', ) # Runs execute() multiple times. ``` -* **Passed values can be of type str, int, float, bytes, None or bool (stored as 1 or 0).** +* **Passed values can be of type str, int, float, bytes, None, or bool (stored as 1 or 0).** ### Example **Values are not actually saved in this example because `'conn.commit()'` is omitted!** @@ -1936,10 +1936,10 @@ with : # Exits the block with commit() ```python # $ pip3 install sqlalchemy from sqlalchemy import create_engine, text - = create_engine('') # Url: 'dialect://user:password@host/dbname'. - = .connect() # Creates a connection. Also .close(). - = .execute(text(''), …) # Replaces ':'s with keyword arguments. -with .begin(): ... # Exits the block with commit or rollback. + = create_engine('') # Url: 'dialect://user:password@host/dbname'. + = .connect() # Creates a connection. Also .close(). + = .execute(text(''), …) # Replaces ':'s with keyword arguments. +with .begin(): ... # Exits the block with commit or rollback. ``` ```text @@ -2832,9 +2832,9 @@ from PIL import ImageDraw .point((x, y)) # Draws a point. Truncates floats into ints. .line((x1, y1, x2, y2 [, ...])) # To get anti-aliasing use Image's resize(). .arc((x1, y1, x2, y2), deg1, deg2) # Draws in clockwise dir. Also pieslice(). -.rectangle((x1, y1, x2, y2)) # To rotate use Image's rotate() and paste(). +.rectangle((x1, y1, x2, y2)) # Also rounded_rectangle(), regular_polygon(). .polygon((x1, y1, x2, y2, ...)) # Last point gets connected to the first. -.ellipse((x1, y1, x2, y2)) # Also rounded_rectangle(), regular_polygon(). +.ellipse((x1, y1, x2, y2)) # To rotate use Image's rotate() and paste(). .text((x, y), , font=) # ` = ImageFont.truetype(, size)` ``` * **Use `'fill='` to set the primary color.** @@ -3340,7 +3340,7 @@ c 6 7 +----------------+---------------+---------------+---------------+ ``` * **All methods operate on columns by default. Pass `'axis=1'` to process the rows instead.** -* **Fifth result's columns are indexed with a multi-index. This means we need a tuple of column keys to specify a single column: `'.loc[row_k, (col_k_1, col_k_2)]'`.** +* **Fifth result's columns are indexed with a multi-index. This means we need a tuple of column keys to specify a column: `'.loc[row_key, (col_key_1, col_key_2)]'`.** #### DataFrame — Multi-Index: ```python @@ -3348,7 +3348,7 @@ c 6 7 = .xs(row_keys, level=) # Rows that have first key on first level, etc. = .set_index(col_keys) # Combines multiple columns into a multi-index. = .stack/unstack(level=-1) # Combines col keys with row keys or vice versa. - = .pivot_table(index=col_key/s, …) # `columns=col_key/s, values=col_key/s`. + = .pivot_table(index=col_key/s, …) # `columns=key/s, values=key/s, aggfunc='mean'`. ``` #### DataFrame — Encode, Decode: diff --git a/index.html b/index.html index bf6a074..dd51771 100644 --- a/index.html +++ b/index.html @@ -55,7 +55,7 @@
- +
@@ -817,15 +817,15 @@ player = Player(point, direction) # -
    -
  • Return value of str() should be readable and of repr() unambiguous.
    • -
  • If only repr() is defined, it will also be used for str().
    • -
  • Methods decorated with '@staticmethod' do not receive 'self' nor 'cls' as their first arg.
    • -
>>> obj = MyClass(1)
 >>> obj.a, str(obj), repr(obj)
 (1, '1', 'MyClass(1)')
+
    +
  • Return value of str() should be readable and of repr() unambiguous.
    • +
  • If only repr() is defined, it will also be used for str().
    • +
  • Methods decorated with '@staticmethod' do not receive 'self' nor 'cls' as their first argument.
    • +

Expressions that call the str() method:

print(<obj>)
 f'{<obj>}'
 logging.warning(<obj>)
@@ -1471,19 +1471,19 @@ CompletedProcess(args=['bc', #JSON
Text file format for storing collections of strings and numbers.
import json
-<str>    = json.dumps(<object>)     # Converts object to JSON string.
-<object> = json.loads(<str>)        # Converts JSON string to object.
+<str>  = json.dumps(<list/dict>)    # Converts collection to JSON string.
+<coll> = json.loads(<str>)          # Converts JSON string to collection.
-

Read Object from JSON File

def read_json_file(filename):
+
Read Collection from JSON File
def read_json_file(filename):
     with open(filename, encoding='utf-8') as file:
         return json.load(file)
 

 
-
Write Object to JSON File
def write_to_json_file(filename, an_object):
+
Write Collection to JSON File
def write_to_json_file(filename, list_or_dict):
     with open(filename, 'w', encoding='utf-8') as file:
-        json.dump(an_object, file, ensure_ascii=False, indent=2)
+        json.dump(list_or_dict, file, ensure_ascii=False, indent=2)
 

 
 
#Pickle
Binary file format for storing Python objects.
import pickle
@@ -1561,33 +1561,33 @@ CompletedProcess(args=['bc', #SQLite
A server-less database engine that stores each database into a separate file.
import sqlite3
-<conn> = sqlite3.connect(<path>)                # Opens existing or new file. Also ':memory:'.
-<conn>.close()                                  # Closes connection. Discards uncommitted data.
+
#SQLite
A server-less database engine that stores each database into its own file.
import sqlite3
+<conn> = sqlite3.connect(<path>)               # Opens existing or new file. Also ':memory:'.
+<conn>.close()                                 # Closes connection. Discards uncommitted data.
 

 
 
-
Read
<cursor> = <conn>.execute('<query>')            # Can raise a subclass of sqlite3.Error.
-<tuple>  = <cursor>.fetchone()                  # Returns next row. Also next(<cursor>).
-<list>   = <cursor>.fetchall()                  # Returns remaining rows. Also list(<cursor>).
+
Read
<cursor> = <conn>.execute('<query>')           # Can raise a subclass of sqlite3.Error.
+<tuple>  = <cursor>.fetchone()                 # Returns next row. Also next(<cursor>).
+<list>   = <cursor>.fetchall()                 # Returns remaining rows. Also list(<cursor>).
 

 
-
Write
<conn>.execute('<query>')                       # Can raise a subclass of sqlite3.Error.
-<conn>.commit()                                 # Saves all changes since the last commit.
-<conn>.rollback()                               # Discards all changes since the last commit.
+
Write
<conn>.execute('<query>')                      # Can raise a subclass of sqlite3.Error.
+<conn>.commit()                                # Saves all changes since the last commit.
+<conn>.rollback()                              # Discards all changes since the last commit.
 

 
-
Or:
with <conn>:                                    # Exits the block with commit() or rollback(),
-    <conn>.execute('<query>')                   # depending on whether any exception occurred.
+
Or:
with <conn>:                                   # Exits the block with commit() or rollback(),
+    <conn>.execute('<query>')                  # depending on whether any exception occurred.
 

 
-
Placeholders
<conn>.execute('<query>', <list/tuple>)         # Replaces '?'s in query with values.
-<conn>.execute('<query>', <dict/namedtuple>)    # Replaces ':<key>'s with values.
-<conn>.executemany('<query>', <coll_of_above>)  # Runs execute() multiple times.
+
Placeholders
<conn>.execute('<query>', <list/tuple>)        # Replaces '?'s in query with values.
+<conn>.execute('<query>', <dict/namedtuple>)   # Replaces ':<key>'s with values.
+<conn>.executemany('<query>', <coll_of_coll>)  # Runs execute() multiple times.
 

 
 
    
-
  • Passed values can be of type str, int, float, bytes, None or bool (stored as 1 or 0).
    • 
+
  • Passed values can be of type str, int, float, bytes, None, or bool (stored as 1 or 0).
    • 
 

 
Example
Values are not actually saved in this example because 'conn.commit()' is omitted!
>>> conn = sqlite3.connect('test.db')
 >>> conn.execute('CREATE TABLE person (person_id INTEGER PRIMARY KEY, name, height)')
@@ -1600,10 +1600,10 @@ CompletedProcess(args=['bc', SQLAlchemy
Library for interacting with various DB systems via SQL, method chaining, or ORM.
# $ pip3 install sqlalchemy
 from sqlalchemy import create_engine, text
-<engine> = create_engine('<url>')               # Url: 'dialect://user:password@host/dbname'.
-<conn>   = <engine>.connect()                   # Creates a connection. Also <conn>.close().
-<cursor> = <conn>.execute(text('<query>'), …)   # Replaces ':<key>'s with keyword arguments.
-with <conn>.begin(): ...                        # Exits the block with commit or rollback.
+<engine> = create_engine('<url>')              # Url: 'dialect://user:password@host/dbname'.
+<conn>   = <engine>.connect()                  # Creates a connection. Also <conn>.close().
+<cursor> = <conn>.execute(text('<query>'), …)  # Replaces ':<key>'s with keyword arguments.
+with <conn>.begin(): ...                       # Exits the block with commit or rollback.
 

 
 
@@ -2305,9 +2305,9 @@ img.show()
 <Draw>.point((x, y))                            # Draws a point. Truncates floats into ints.
 <Draw>.line((x1, y1, x2, y2 [, ...]))           # To get anti-aliasing use Image's resize().
 <Draw>.arc((x1, y1, x2, y2), deg1, deg2)        # Draws in clockwise dir. Also pieslice().
-<Draw>.rectangle((x1, y1, x2, y2))              # To rotate use Image's rotate() and paste().
+<Draw>.rectangle((x1, y1, x2, y2))              # Also rounded_rectangle(), regular_polygon().
 <Draw>.polygon((x1, y1, x2, y2, ...))           # Last point gets connected to the first.
-<Draw>.ellipse((x1, y1, x2, y2))                # Also rounded_rectangle(), regular_polygon().
+<Draw>.ellipse((x1, y1, x2, y2))                # To rotate use Image's rotate() and paste().
 <Draw>.text((x, y), <str>, font=<Font>)         # `<Font> = ImageFont.truetype(<path>, size)`
 

 
@@ -2720,13 +2720,13 @@ c  6  7
 
 
    
 
  • All methods operate on columns by default. Pass 'axis=1' to process the rows instead.
    • 
-
  • Fifth result's columns are indexed with a multi-index. This means we need a tuple of column keys to specify a single column: '<DF>.loc[row_k, (col_k_1, col_k_2)]'.
    • 
+
  • Fifth result's columns are indexed with a multi-index. This means we need a tuple of column keys to specify a column: '<DF>.loc[row_key, (col_key_1, col_key_2)]'.
    • 
 

 
DataFrame — Multi-Index:
<DF>   = <DF>.xs(row_key, level=<int>)         # Rows with key on passed level of multi-index.
 <DF>   = <DF>.xs(row_keys, level=<ints>)       # Rows that have first key on first level, etc.
 <DF>   = <DF>.set_index(col_keys)              # Combines multiple columns into a multi-index.
 <S/DF> = <DF>.stack/unstack(level=-1)          # Combines col keys with row keys or vice versa.
-<DF>   = <DF>.pivot_table(index=col_key/s, …)  # `columns=col_key/s, values=col_key/s`.
+<DF>   = <DF>.pivot_table(index=col_key/s, …)  # `columns=key/s, values=key/s, aggfunc='mean'`.
 

 
 
DataFrame — Encode, Decode:
<DF> = pd.read_json/html('<str/path/url>')     # Run `$ pip3 install beautifulsoup4 lxml`.
@@ -2923,7 +2923,7 @@ $ deactivate                # Deactivates the active