Python/Syntax: Difference between revisions

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Or we can use the following syntax to pass values for each one:
Or we can use the following syntax to pass values for each one:
  kwarg_func(my_var=True, my_int=555, some_string='This is the a different string.')
  kwarg_func(my_var=True, my_int=555, some_string='This is a different string.')


Note that we can also do any combination thereof, where we leave some values as the defaults, but override others.
Note that we can also do any combination thereof, where we leave some values as the defaults, but override others.

Revision as of 11:26, 27 December 2020

Unlike most other languages, Python attempts to be simplistic in syntax design.
Thus, there are no semicolons to indicate a line end, and there are no brackets.
However, indentation is very important, and Python raises syntax errors without proper indentation.

Syntax Styling

Python recommends following the official PEP-8 guidelines for code styling.
Note that PEP-8 is ultimately just a suggestion, and can be adapted for your needs. The most important part is to be consistent internally, within each individual project.

Of note though:

  • PEP-8 recommends using spaces over tabs, for indentation.
    • Note though, that either is technically okay, but combining the two in one file will result in syntax errors.
  • PEP-8 recommends 79 character maximum line length. But this is frankly really small now of days, particularly as screen sizes grow larger.
    • Instead, we recommend following PyCharm's default of 120 characters per line, maximum.
  • PEP-8 recommends removing trailing whitespaces and adding a blank line at the end of each file.


Comments

Inline Comments

# This is an inline comment.

Block Comments

"""
This is a block comment.
Comment line 2.
Another block comment line.
"""

Block/Region Declaration

Regions are used for organizational purposes, and allow for code folding at the click of a button. To be useful, both the start and end must be declared.

#region MyRegionName
 
...
 
#endregion MyRegionName


Variables

Variables are weakly typed in Python. That means you can just declare a variable name, and Python will automagically figure out what typing it is.

Variable Definition

a_bool = True
b_bool = False
my_var_1 = "This is "
my_var_2 = "a string."

Variable Usage

print('Printing variable values'.)
print(a_bool)
print(b_bool)
print('{0}{1}'.format(my_var_1, my_var_2))

Booleans

Python uses the following bools:

true_bool = True
false_bool = False

Null Values

Python uses None in place of the standard null:

null_var = None

If Statements

Note that Python uses and to replace the standard &&, and or to replace the standard {{ ic |||}.

Basic If

if x == y:
    # Logic if true.

Full If

if x == y:
    # Logic if true.
elif x and (y or z):
    # Logic for "else if" true.
else:
    # Logic for false.

Switch/Case Statements

Surprisingly, Python does not support case statements. Instead, Python officially recommends just using if statements to accomplish the equivalent.


Functions

Basic Template

def <function_name>(<args>, <kwargs>):
    """"
    Function description here.
    :param <variable_name>: <variable_description>
    :return: <return_val_description>
    """
    # Function logic here.

    ...

    # If function has a return value, then return it with the following.
    return <variable_here>

Examples

Basic example:

def my_func():
    # Function logic here.

Example with "arg" arguments:

def arg_func(my_int, my_string, some_other_arg):
    # Function logic here.

Example with "kwarg" arguments:

def kwarg_func(my_var=None, my_int=12345, some_string='This is the default value.'):
    # Function logic here.

Args and Kwargs

"Args" and "Kwargs" are fancy ways to say "variables with a default" and "variables without a default".

Note that in function declaration, arg values must always come before kwarg values.

Args

To show, in the "arg" example above, we have my_int. This is an "arg" because it does not have an equal sign next to it.

Effectively, this means the variable must be provided into the function, or a syntax error will raise.

To call the function in the above "arg" example, we use the following syntax:

arg_func(12345, 'This is a string.', True)

Kwargs

Meanwhile, in the "kwarg" example above, we have "my_int" again, but it looks like this my_int=12345. The equal sign means it's a "kwarg".

Effectively, a kwarg is an optional argument, in that you can call the function without specifying it. In such a case, the kwarg will take on the value after the equal sign, as a default. However, if you do pass a value for the kwarg, then it will use that value instead of the default.

To call the function in the above "kwarg" example, we use the following syntax to use default values:

kwarg_func()

Or we can use the following syntax to pass values for each one:

kwarg_func(my_var=True, my_int=555, some_string='This is a different string.')

Note that we can also do any combination thereof, where we leave some values as the defaults, but override others.