Python Fundamentals

This contains all the basic topics of Python

Python is an interpreted, object-oriented, high-level programming language with dynamic semantics. Its high-level built in data structures, combined with dynamic typing and dynamic binding, make it very attractive for Rapid Application Development, as well as for use as a scripting or glue language to connect existing components together.

What can be done with Python?

General Web Development
Scientific Computing / Data Science
Machine Learning
Automation and Scripting
Web Scraping
build games

Install Python:

To install Python, follow these steps:

Navigate to the Python downloads page: Python downloads.
Click on the link/button to download Python 3.x or Python 2.7
Follow the installation instructions.
Open your terminal again and type the command python. The Python interpreter should respond with the version number.

e.g. on windows:

Python 3.7.4 (tags/v3.7.4:e09359112e, Jul  8 2019, 20:34:20) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

How to do "Hello world" in Python?

# this is a comment
print("Hello World")

Variables

number = 10  # This a variable

PI = 3.14159  # This is a constant

Data type

Python has the following data types built-in by default, in these categories:

Category	Data type
Text Type	str
Numeric Types	int, float, complex
Boolean Type	bool
Sequence Types	list, tuple, range
Mapping Type	dict
Set Types	set, frozenset
Binary Types	bytes, bytearray, memoryview

Primitive data structures	Non-primitive data structures
Integers, Float, strings, Boolean	Arrays, Lists, Tuples, Dictionary, Sets, Files

Built-in Data Structures

Lists

my_list = ['First', 'Second', 'Third', True, 21, 10.5]
length = len(my_list)  # Length of the list

List Methods

Method	Description
append(x)	Add an item to the end of the list. Equivalent to `a[len(a):] = [x]`.0
insert(iterable)	Insert an item at a given position. The first argument is the index of the element before which to insert, so `a.insert(0, x)` inserts at the front of the list, and `a.insert(len(a), x)` is equivalent to `a.append(x)`.
extend(i, x)	Extend the list by appending all the items from the iterable. Equivalent to `a[len(a):] = iterable`.
remove(x)	Remove the first item from the list whose value is equal to x. It raises a `ValueError` if there is no such item.
pop([i])	Remove the item at the given position in the list, and return it. If no index is specified, `a.pop()` removes and returns the last item in the list.
clear()	Remove all items from the list. Equivalent to `del a[:]`.
index(x [, start [, end ] ])	Return zero-based index in the list of the first item whose value is equal to x. Raises a `ValueError` if there is no such item.
count(x)	Return the number of times x appears in the list.
sort(*, key=None, reverse=False)	Sort the items of the list in place.
reverse()	Reverse the items of the list in place.
copy()	Return a shadow copy of the list. Equivalent to `a[:]`.

Tuples

my_tuple = (3, 5, 6, 3, 7)

Tuple methods

Method	Description
count(x)	Return the number of items x appers in the tuple.
index(x [, start [, end ] ])	Return zero-based index in the tuple of the first item whose value is equal to x. Raises a `ValueError` if there is no such item.

Sets

my_set = {3, 4, 5, 6, 7, 2, 2}  # duplicate items are removed, then the set is {2, 3, 4, 5, 6, 7}

Set methods

Method	Description
add(x)	Adds a given element to a set. If the element is already present, it doesn't add any element. `add()` method takes a single parameter:
clear()	Removes all elements from the set. It doesn't take any parameters.
copy()	Returns a shallow copy of the set. It doesn't take any parameters.
pop()	Removes an arbitrary element from the set and returns the element removed. It doesn't take any arguments.
remove(x)	Removes the specified element from the set. It takes a single element as an argument and removes it from the set.
discard(x)	Takes a single element x and removes it from the set (if present).
difference(set)	Returns the difference between two sets which is also a set. It doesn't modify original sets.
difference_update(set)	Updates the set calling `difference_update()` method with the difference of sets.
intersection([ set [ , ... ] ])	Returns a new set with elements that are common to all sets. Allows arbitrary number of arguments (sets).
intersection_update([ set [ , ... ] ])	Updates the set calling `intersection_update()` method with the intersection of sets.
union([ set [ , ... ] ])	Returns a new set with elements from the set and all other sets (passed as an argument).
symmetric_difference(set)	Returns the symmetric difference of two sets.
symmetric_difference_update(set)	Finds the symmetric difference of two sets and updates the set calling it.
update([ iter [ , ... ] ])	Updates the set, adding items from other iterables.
issubset(set)	Returns `True` if all elements of a set are present in another set (passed as an argument). If not, it returns `False`.
issuperset(set)	Return `True` if all elements of another set is present in the current set (method caller). If not, it returns `False`.
isdisjoint(set)	Return `True` if two sets are disjoint sets. If not, it returns `False`.

Dictionaries

my_dict = {'name': 'Leo', 'age': 22} # {key:value,}

Dictionary methods

Method	Description
clear()	Removes all items from the dictionary.
copy()	Returns a shallow copy of the dictionary.
get(key [ , other ])	Returns the value of the `key` if this doesn't exist returns `other` that it's `None` for default.
items()	Returns a new object of the dictionary's items in (key, value) format.
keys()	Returns a new object of the dictionary's keys.
values()	Returns a new object of the dictionary's values
pop(key [ , other ])	Removes the item with the `key` and returns its value or `other` if `key` is not found. If `other` is not provided and the `key` is not found, it raises `KeyError`.
popitem()	Removes and returns an arbitrary item (key, value). Raises `KeyError` if the dictionary is empty.
update( [ other ] )	Updates the dictionary with the key/value pairs from `other`, overwriting existing keys.
fromkeys( sequence, [ , values ] )	Returns a new dictionary with the given sequence of elements as the keys of the dictionary.
setdefault(key [ , default_value ])	Returns the value of a key (if the key is in dictionary). If not, it inserts key with a value to the dictionary.

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