Python Syntax


1. Python Comment


The # symbol is used for comments in python. In most editors keyboard shortcut to comment/uncomment is Ctrl + /. However, Python IDLE uses Alt + 3 to comment and Alt + 4 to uncomment.

>>> x = 10                # this is a comment


2. Semicolon in Python Syntax


; exists in Python with the same meaning of line termination or line separation. However, \n is more frequently used for line termination.

>>> a = 1; b = 2

>>> a, b = 1, 2 


3. Multiple Assignments


It is possible to assign multiple variables to multiple values respectively in python.

>>> x, y, z = 1, 2.3, "hello"

>>> a = b = c = 0


4. Swapping


Multiple assignments make swapping very easy in Python and a temporary variable is never needed.

>>> x, y = y, x


5. Case Sensitive


Python is a case-sensitive language and changes in case results into a new object.

>>> 'a' == 'A'
False


6. Use Of Quotes In Python


Quotes are used in python to define string objects. There are four categories of quotes that can be used:

>>> 'a' == "a" == '''a''' == """a"""
True

>>> '''INSERT INTO TABLE VALUES("John's Car")'''

>>> """ Multi-line 
    string
    """

7. Use Of Backslash


can be prefixed before special characters to treat them as normal characters.

'C:\\Users\\Programink\\Desktop'


\ can also be used for line continuation.


>>> x = 1 + 2 \
    3
>>> x
6


8. Nomenclature


Naming identifiers in Python must obey these three rules:

1) It must consist of only A-Za-z0-9_

2) It must not begin with any digit 0-9

3) It must not be a keyword. To check the keywords run:


>>> import keyword
>>> print(keyword.kwlist)


>>> x1 = "hello" # valid
>>> 3m = "hello" # invalid


9. Indentation


Simple left padding acts as a block definition in Python. It is typically a tab space or four white space in the beginning of an enclosed statement.

def greeting():
    print("Welcome to Programink")


10. Underscore '_'


_ is used in multiple different ways in python.

a) In interactive mode underscore _ refers to the last computed values.

b) One underscore _ at the beginning of the variable name indicates that the variable will become private later on.

c) Two underscores __ before an attribute name makes it private.

d) Two underscores on either side of the attribute name symbolize weak attribute and it is read as 'dunder'. Eg. __name__

>>> x = 10
>>> _ + 1
11