Autosave: 2023-02-15 15:31:31

Programming_Languages/Python/Syntax/Dictionaries_in_Python.md

@@ -14,3 +14,113 @@ Dictionaries:
 - Are mutable
 - Are indexed by a key which references a value
 - Can be increased/decreased in length by adding/removing new members.
+
+## Basic usage
+
+Dictionaries are declared with `{...}`:
+
+```python
+cities = {
+  'Wales': 'Cardiff',
+  'England': 'London',
+  'Scotland': 'Edinburgh',
+  'Northern Ireland': 'Belfast',
+  'Ireland': 'Dublin'
+}
+
+print(type(citites))
+# <class 'dict'>
+```
+
+## Accessing entries
+
+```python
+print(cities['Wales'])
+# Cardiff
+
+print(cities.get('Ireland'))
+# Dublin
+
+print(cities.values())
+# ['Cardiff', 'London', 'Edinburgh', 'Belfast', 'Dublin']
+
+print(cities.keys())
+# ['Wales', 'England', 'Scotland', 'Northern Ireland', 'Ireland']
+
+print(cities.items())
+# [('Wales', 'Cardiff'), ('England', 'London'), ('Scotland', 'Edinburgh'), ('Northern Ireland', 'Belfast'), ('Ireland', 'Dublin')]
+```
+
+## Predicates
+
+```py
+print('Wales' in cities)
+# True
+
+print('France' not in cities)
+# True
+```
+
+## Looping
+
+```py
+for country in cities:
+    print(country, end=', ')
+    print(cities[country])
+
+"""
+Wales, Cardiff
+England, London
+Scotland, Edinburgh
+Northern Ireland, Belfast
+Ireland, Dublin
+"""
+
+for e in country.values():
+    print(e)
+```
+
+## Updating values
+
+```py
+cities['Wales'] = 'Swansea'
+print(cities)
+```
+
+## Removing values
+
+```py
+# Remove last item
+cities.popitem()
+print(cities)
+# {'Wales': 'Cardiff', 'England': 'London', 'Scotland': 'Edinburgh', 'Northern Ireland': 'Belfast'}
+
+# Remove specific entry by key
+
+cities.pop('Northern Ireland')
+print(cities)
+# {'Wales': 'Cardiff', 'England': 'London', 'Scotland': 'Edinburgh'}
+
+del cities['Scotland']
+print(cities)
+{'Wales': 'Cardiff', 'England': 'London'}
+```
+
+## Containers as values
+
+```py
+seasons = {
+'Spring': ('Mar', 'Apr', 'May'),
+'Summer': ('June', 'July', 'August'),
+'Autumn': ('September', 'October', 'November'),
+'Winter': ('December', 'January', 'February')}
+
+print(seasons['Spring'])
+print(seasons['Spring'][1])
+
+"""
+('Mar', 'Apr', 'May')
+Apr
+"""
+
+```

Programming_Languages/Python/Syntax/Functions_in_Python.md

@@ -0,0 +1,124 @@
+---
+categories:
+  - Programming Languages
+tags: [python]
+---
+
+# Functions
+
+- Convention is to leave a double line-break after a function definition (but not with nested functions - here, a single linebreak is sufficient)
+- Scope within functions is demarcated by indents, as everything in Python
+- We use a docstring _within_ the function body, to document our function. This text will then show up in Intellisense etc.
+
+## Basic examples
+
+```py
+
+# No params, no return
+def print_msg():
+    """ A function that prints hello world """
+    print('Hello World!')
+
+print_msg()
+# Hello World!
+
+print(type(print_msg))
+# <class 'function'>
+
+# Params, no return
+def print_my_msg(msg):
+    """ A simple function to print a message """
+    print(msg)
+
+print_my_msg('Good day')
+# Good day
+
+# Params and return
+def square(n):
+    return n * n
+
+print(square(2))
+# 4
+
+result = square(4)
+print(result)
+
+# 16
+
+```
+
+## Default parameters
+
+```py
+def greeter(name, message='Live Long and Prosper'):
+    print('Welcome', name, '-', message)
+
+greeter('Eloise')
+
+# Welcome Eloise - Live Long and Prosper
+```
+
+## Function with arbitrary parameter list
+
+```python
+def greeter(*args):
+    for name in args:
+        print('Welcome', name)
+
+greeter('John', 'Denise', 'Phoebe', 'Adam', 'Gryff', 'Natalia')
+
+"""
+Welcome John
+Welcome Denise
+Welcome Phoebe
+Welcome Adam
+Welcome Gryff
+Welcome Natalia
+"""
+```
+
+## Scoping
+
+Function variables are locally scoped by default.
+
+They can access variables that are outer to them and can redefine them within their own scope _and_ within the global scope using the keywords `global` and `nonlocal`.
+
+Below a global variable is accessed and changed but only internally within a function scope
+
+```py
+max = 100
+print('initial value of max:', max)
+
+def print_max():
+    global max
+    max = max + 1
+    print('inside function:', max)
+
+
+print_max()
+print('outside function:', max)
+
+"""
+initial value of max: 100
+inside function: 101
+outside function: 101
+"""
+```
+
+Below a higher-scoped variable is redefined from within the lower scope:
+
+```py
+def myfunc1():
+  x = "John"
+  def myfunc2():
+    nonlocal x
+    x = "hello"
+  myfunc2()
+  return x
+
+print(myfunc1())
+
+# hello
+```
+
+We cannot however redefine a global variable from a function scope permanently. It will remain whatever it is in global scope, after the function has run.

Programming_Languages/Python/Syntax/Lambdas_in_Python.md

@@ -0,0 +1,33 @@
+---
+categories:
+  - Programming Languages
+tags: [python]
+---
+
+# Lambdas in Python
+
+In Python, anonymous functions like arrow-functions in JavaScript (`() => {}`) are immediately invoked and unnamed. They are called lambdas.
+
+Whilst they are unnamed, just like JS, the value they return can be stored in a variable. They do not require the `return` keyword.
+
+They are most often used unnamed with the functional methods [map, filter and reduce](/Programming_Languages/Python/Syntax/Map_filter_reduce_in_Python.md)
+
+Here is the two syntaxes side by side:
+
+```js
+const double = (x) => x * x;
+```
+
+```py
+double = lambda x: x * x
+```
+
+Here is a lambda with multiple parameters:
+
+```py
+func = lambda x, y, z: x + y + z
+print(func(2, 3, 4))
+# 9
+```
+
+> Lambdas obviously enshrine functional programming paradigms. Therefore they should be pure functions, not mutating values or issueing side effects. For example, it would be improper (though syntactically well-formed) to use a lambda to `print` something

Programming_Languages/Python/Syntax/Map_and_filter_in_Python.md

@@ -0,0 +1,55 @@
+---
+categories:
+  - Programming Languages
+tags: [python]
+---
+
+# Map and filter in Python
+
+## Map
+
+```py
+data = [1, 3, 5, 2, 7, 4, 10]
+
+new_data = map(lambda i: i + 10, data)
+print(new_data)
+```
+
+We can also pass-in a function rather than use a lambda:
+
+```py
+def add_one(i):
+    return i + 1
+
+x = list(map(addOne, data))
+# [2, 4, 6, 3, 8, 5, 11]
+# necessary to add `list` to get some output
+```
+
+## Filter
+
+```py
+data = [1, 3, 5, 2, 7, 4, 10]
+
+d1 = list(filter(lambda i: i % 2 == 0, data))
+print(d1)
+#  [2, 4, 10]
+
+def is_even(i):
+    return i % 2 == 0
+
+
+# Filter for even numbers using a named function
+d2 = list(filter(is_even, data))
+
+# [2, 4, 10]
+```
+
+## Chaining
+
+```py
+data = [1, 3, 5, 2, 7, 4, 10]
+new_data = list(map(lambda i: i + 10, filter(is_even, data)))
+print(new_data)
+# new_data: [12, 14, 20]
+```

Programming_Languages/Python/Syntax/Sets_in_Python.md

@@ -54,6 +54,37 @@ basket.remove('apple')
 basket.discard('apricot')
 print(basket)
 # {'pear', 'banana', 'orange'}
+
+basket.clear()
+print(basket)
+#set
+
 ```
 
 ## Add items to a set
+
+```python
+basket.add('apricot')
+print(basket)
+# {'apricot', 'pear', 'banana', 'orange'}
+```
+
+## Apply unions and intersections
+
+```python
+s1 = {'apple', 'orange', 'banana'}
+s2 = {'grapefruit', 'lime', 'banana'}
+print('Union:', s1 | s2)
+# Union: {'apple', 'orange', 'grapefruit', 'lime', 'banana'}
+
+print('Intersection:', s1 & s2)
+# Intersection: {'banana'}
+
+
+print('Difference:', s1 - s2)
+# Difference: {'orange', 'apple'}
+
+print('Symmetric Difference:', s1 ^ s2)
+#Symmetric Difference: {'apple', 'orange', 'grapefruit', 'lime'}
+
+```

_meta/Topic_Log.md

@@ -2,17 +2,24 @@
 
 ## Python
 
-- Get PEP8 working in VSCode as linter and add to execute on save. (These are conventions not syntactic enforcements, style)
-
-- Is there a thing like prettier to enforce double quotes over single for instance?
-
-- Research: How do I make sure I am using `conda` and not the default install in VSCode ? PyCharm makes it easy to select environment.
-
 - Research: best practice for separating projects into `conda` environments like npm
 
 - Read-up more on types: what does it mean for Python to be dynamically typed. What is type-hinting really?
+
   - Use provided pdfs and John's books
 
+- Is `dictionary.values()`/ `dictionary.keys()` of type list?
+- Is `dictionary.items()` a list of tuples for key, value?
+
+- How to run test suites via VSCode?
+
+  BBC Course, remaining topics:
+
+  - Classes and object-oriented paradigms in Python
+  - Modules
+  - Error handling
+  - Testing
+
 ## Bash
 
 - Best way to run a command in a script - is it to `echo` it?