python-sep-2022
Python exercises on topics covered in Sanjay Vyas's Deep python course in Sep-2022 Attended Deep python workshop by Sanjay Vyas Sir, here are my notes from the session :
----------- Day 1 -------------------
Python:
Memory MAnagement
Interpreter
JIT Compiler
Garbage collector
Variable declared are not global or local they are both
Each Function call creates its own Stack frame
Each stack frame has its own dictionary
Checking the type (static programming ) and not checking in Type (dynamic programming)
Better comments configuration:
"better-comments.tags": [
{
"tag": "!",
"color": "#FF2020",
},
{
"tag": "~!",
"color": "#FFFFFF",
"backgroundColor": "#FF2020",
},
{
"tag": "_",
"color": "#FF2020",
"underline": true
},
{
"tag": "-",
"color": "#FF2D00",
"strikethrough": true,
},
{
"tag": "^",
"color": "#CD607E",
},
{
"tag": "~^",
"color": "#FFFFFF",
"backgroundColor": "#CD607E",
},
{
"tag": "?",
"color": "#0096FF",
},
{
"tag": "~?",
"color": "#FFFFFF",
"backgroundColor": "#0096FF",
},
{
"color": "#75757",
"tag": "//",
},
{
"color": "#FF8C00",
"tag": "%",
},
{
"tag": "~%",
"color": "#FFFFFF",
"backgroundColor": "#FF8C00",
},
{
"tag": "*",
"color": "#66FF66",
},
{
"tag": "~*",
"color": "#FFFFFF",
"backgroundColor": "#29AB87",
},
{
"tag": "#",
"color": "#FFFF00",
},
{
"tag": "~#",
"color": "#000000",
"backgroundColor": "#FFFF00",
},
{
"tag": ">",
"color": "#00FFFF",
},
{
"tag": "~>",
"color": "#000000",
"backgroundColor": "#00FFFF",
}
----------- Day 2 -------------------
Language have a pattern
- Type System -- Static or Dynamic both of them have type system
- Operators -- + = >
- Control Flow -- Conditional, Loops, Switch
- Function -- Abiliti to write a function
- Object Oriented -- Class
- Functional -- f(x)-> x * x
Principles of Object Oriented
There are no native types in pure OOP language, even Integer is a class
Native data types are single unit
Objects are supposed to be opaque
SmallTalk has classes but no public private
pharo.org for building classes in SmallTalk
Communication happens through messages
Objects are supposed to be composite
C++, Java, C# are hybrid OOP language
One can define classes but there are also Native types, so one can creat object and can create variables
Public, Private and Protected
Even in Python everything is an object
Communication happens through message passing AT RUNTIME
Objects are not OPAQUE in case of Python
Types in Python
-
bool
-
int
-
float
-
complex
-
string
-
list
-
tuple
Python has no native types but instead we call them as Basic Datatypes as they are classes
Control Flow
Alter the sequence of program
No code blocks but indentation which defines the scope of the code
For python the control flow is mainly :
-
if,
-
for,
-
while
: does the job of establishing code block
; is a python separator which is used to write multiple lines of code in same line
id() can be used to determine the equivalence of the objects in terms of both being the same object
----------- Day 3 -------------------
Expressions are assigned and consumed, also they emit a value which can be consumed by someone
1
a=1
b = a = 1
Statements are actions and not values
if a == 1:
pass
for a in range(0, 11):
pass
if you one tries to asign statement to expression the there is an error
which says "Expresssion expected to the right of ="
Pascal Case : first letter of english word is capitalized
Camel Case: first charater of english word is lower case
Snake Case: english word followed bu underscore - def day_of_week (Used by Python)
Kebab Case: english word followd by the hyphen (-) --> webkit-toolkit- (Used in HTML classes and in CSS)
while can be paired with else to identify if the loop completed
while a < b:
# conditions
if a == b : break # If break happens then the else part does not kick in,
# while having continue still executes the else part and contiues the loop too.
else:
# this is done only if the loop was not broken
----------- Day 4 -------------------
init is called once the object is created
first parameter of init is self which points to current object, it can be named as anything self is just a variable name.
Same class can be written as part of the class
Monkey patching --> Insert a function inside an obejct at run time,
def hello():
print("hello")
p.hello = hello
p.hello()
q = Person()
q.bye()
q.hello()
Every thing in a class is a dictionary, assigning a function to a variable
is nothing but assigning a funtion body to the key.
Key can be a name while value can be function body or anything
Can Monkey patching be done at Class Level ?
Answer is yes the it can be done using the setattr(ClassName, "Method_name", method_definition)
print(locals()) --> This print locals
----------- Day 5 -------------------
mypy is a tool which is used to check the types statically in Python
mypy will flag the monkey patching as errors but the code will still run
python3 -m pip install mypy
mypy filename --> is the command which can run a static type checking
When we create a class python creates a PyClass object
When deriving a class the first parameter of class definition is super which is base class :
class SavingsAccount(Account)
Class which is the owner of the field should initiaize the field
super() is a function in python which refers to the base class, it can be used refer the constructor of base class :
super().init(self, base class init params )
----------- Day 6 -------------------
simple array in python is not a contiguous location of memory
Internally its a type of linked list, with one node pointing to another
in the latest version of python there is a Array class which has contiguous memory
Different methods attached to the list
Python can create mixed type list like [1, "Guido", True, 1], but python is strongly typed because it will not
allow to add 2 different types but C can do it by implicitly conerting the data.
import array from array # creates a contiguous memory array
Lists are less performant than array, hence new version explicitly introduced array
Map operations --> Hash Tables --> Dictionary
----------- Day 7 -------------------
Constructor chaining
The logic to update a field should be present in the class which owns the class
super().withdraw() --> to call the base class method
Memory management in Python
C, Pascal, C++ --> Manual Memory Management
Python uses --> Reference Counting, when one adds reference to an object the refCount += 1
Every time a new reference is pointed to same object the ref count is incremented by 1
Also known as Automatic Reference Counting (ARC)
For every object Python holds its own reference hence the ref count starts at 1
Python has RefCount GC and Generational GC
Mark-Sweep-Compact GC used by Java, C#,
----------- Day 8 -------------------
string.format library: https://docs.python.org/3/library/string.html
print("name [{0:^20s}] {1:o}").format(name, 14) --> first positional parameter center it in 20 charaacter and print it as a string
specifying f in front of a string in python makes it as a format string which we specified above
str is the same as toString in C#
implementing str for a class will help in printing the method
there is another method repr(object) --> Representation of the object
which also calls the repr which should present the representation of the object
repr shows how the object was created --> Something similar to reflection
Operators are te reak workhorses of programming
+, ==, > , < are the examples of operators
to overload the operator == use the dunder method eq
operator overloading
maps to gt
< maps to lt
!= maps to ne
= maps to ge
<= maps to le
Defining the eq and gt will also cater to implementing the lt
it will do a not of the greater than
- maps to add (Add)
+= maps to iadd (Plus equal to)
- maps to sub (Subtract)
-= maps to isub (Minus equal to)
----------- Day 9 -------------------
built-in data structures in python
list - modification (insert, remove)
set (unique)
dictionary key:value pairs, unique keys
tuple - readonly quick record, tuple requires a comma to be considered as a tuple
otherwise with single it will be considered as the type of the element, read only quick record
ternary operator --> Condition ? when-true: when-false
--> when-true Condition else when-false
return label if label is not None else "Unknown"
Python dictionaries are always ordered since Python 3.8
Default params have to be the last params the and can be followed by default params only
Variadic parameter (var-args or rest arguments) use * represents that there can be any number of arguments,
the name args can be changed, it's a convention
----------- Day 10 -------------------
Decorator is an function which will call your function, it takes the function as a param to which it is applied
It must return a function to which it is called
When you pass a parameter to decorator it becomes decorator factory and the decorator function is indented one level more
Inbuilt decorators like
@staticmethod to mark methods as static method
@property
@balance.setter --> Property setter
Generators yield out the transactions