I am not the best at learning stuff unless there is a
very good reason to learn it. I have been meaning to learn Python for a while
but lacking sufficient motivation. Now I have a very good reason - I need to
use Python within Mulesoft to develop Mulesoft Applications. Time to start
learning! These notes come from some PDFs I stumbled across, and - on-first-glance
- they looked like a very good beginners introduction to Python. I should point
out that taking notes is the best way I learn. If I just read stuff, I tend to
zone out and learn nothing.
1) Python Introduction
Python was developed by Guido van Rossum who
started implementing Python in 1989.
Python is named after the comedy television show ‘Monty
Python’s Flying Circus’.
To install Python on your operating system, go to:
Python is an interpreted programming language. You write
Python (.py) files in a text editor and then put those files into the
python interpreter to be executed. Example:
C:\Users\You>
python helloworld.py
You can practice with Online IDE:
2) Python Syntax
2.1) Print Function
The print() function prints the specified message
to screen or other standard output device.
print("Hello
World")
A string is a collection of characters inside “Double
quotes” or ‘Single quotes’ (you can use ‘Single quotes’ inside “double quotes”
and vice versa.)
2.2) Escape Sequences
and Raw String
To insert characters that are illegal in a string, use
the escape character \ followed by the character you want to insert. For
example:
print("Hello
\"World\" World")
Image: Example: Hello "World" World (using onlinegdb)
More escape sequences used in Python:
\' = Single Quote
\" = Double Quote
\\ = Backslash
\n = New line
\t = Tab
\b = Backspace (delete the letter before ‘\b’)
Raw string notation (r"text")
keeps regular expressions meaningful and confusion-free. Example:
print(r"Line
A \nLine B")
Output:
Line A \nLine
B
2.3) Comments
A hash sign (#)
that is not inside a string literal begins a comment.
Python does not really have syntax for multi-line
comments. Python will ignore string literals that are not assigned to a
variable, so you can add a multiline string (triple quotes) in your code and
place your comment inside it:
"""
This is a
multi-line
comment
"""
2.4) Python Basic
Operators
Python Arithmetic Operators:
+ | Addition
- | Subtraction
* | Multiplication
/ | Division
% | Modulus
** | Exponent
// | Floor
Division
Python Comparison Operators:
== | Is equal to
!= | Is not equal
to
<> | Is not
equal to (similar)
> | Greater than
< | Less than
>= | Greater
than or equal to
<= | Less than
or equal to
Python Assignment Operators (with equivalents):
= | Simple
assignment
+= | Add AND assignment (c = c + a)
-= | Subtract AND assignment (c = c - a)
*= | Multiple AND assignment (c = c * a)
/= | Divide AND assignment (c = c / a)
%= | Modulus AND assignment (c = c % a)
**= | Exponent
AND assignment (c = c ** a)
//= | Floor
division AND assignment (c = c // a)
Python Logical Operators:
and
or
not
2.5) Python as a
Calculator
Image: 4/2 = 2.0 and 4//2 = 2 (integer division)
Round Function
The round() function returns a floating-point
number that is a rounded version of the specified number, with the specified
number of decimals.
Syntax: round(number,digits)
number: Required - number to be rounded.
digits: Optional - number of decimals to use when
rounding (default is 0)
Precedence Rule
To evaluate complex expressions, python follows the rule
of precedence which governs the order in which the operation takes place.
Operator | Precedence
and Associativity rule
------------+----------------------------------
Parentheses |
Highest
Exponential | Right
to left
* / // % | Left to right
+ - | Left to right
2.6) Variable in Python
Creating Variables
Python variables do not need explicit declaration to reserve
memory space. The declaration happens automatically when you assign a value to
a variable (using = etcetera). Python has no command for declaring a variable.
Variables do not need to be declared with any type and can even change type
after they have been set. String variables can be declared either by using
single or double quotes.
Rules for Python Variable Names
- must start with a letter or the underscore character
- cannot start with a number
- can only contain alpha-numeric characters and
underscores (A-z, 0-9, and _)
- are case-sensitive
Assign Value to Multiple Variables
Example:
x, y, z = "Orange",
"Banana", "Cherry"
print(x)
print(y)
print(z)
Orange
Banana
Cherry
x = y = z = "Orange"
print(x)
print(y)
print(z)
Orange
Orange
Orange
2.7) Basic Built-in
Data Types
Python has various standard data types that are used to
define the operations possible on them. Python standard data types:
Text type : str
Numeric types : int,
float, complex
Sequence types: list,
tuple, range
Mapping type : dict
Set types : set, frozenset
Boolean type : bool(True, False)
Binary types : bytes, bytearray, memoryview
String (Str): A string value.
Integer (int):
Positive or negative whole numbers.
Float (float): Any real number with a floating-point
representation.
Complex number (complex): A number with a real and
imaginary component represented as x +yj where x and y are floats and j is the
square root of -1 (imaginary number)
Boolean: True or False (Note: ‘T’ and ‘F’ are
capitals. ‘true’ and ‘false’ are not valid Booleans.)
List []: An ordered collection of one or more data
items, not necessarily of the same type.
Tuple (): An ordered collection of one or more
data items, not necessarily of the same type.
Note: The main difference between lists and tuples is
the fact that lists are mutable whereas tuples are immutable.
2.8) Getting the Data
Type
Example:
print(type(1234))
print(type(55.50))
print(type(6+4j))
print(type("hello"))
print(type([1,2,3,4]))
print(type((1,2,3,4)))
Image: Output demonstrating type() from above example -
int,float,complex,str,list,tupe
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