Some Python Tips and Tricks

These can help you writer better (or at least more pythonic) code.

Escape characters

Escape character	Description
\\	Backslash
\'	Single quote
\"	Double quote
\a	ASCII bell (BEL)
\b	ASCII backspace (BS)
\f	ASCII formfeed (FF)
\n	ASCII linefeed (LF)
\N{name}	Character named name in the Unicode database (Unicode only)
\r	ASCII carriage return (CR)
\t	ASCII horizontal tab (TAB)
\uxxxx	Character with a 16-bit hex value xxxx (Unicode only)
\Uxxxxxxxx	Character with a 32-bit hex value xxxxxxxx (Unicode only)
\v	ASCII vertical tab (VT)
\ooo	Character with octal value oo
\xhh	Character with hex value hh

String formatting

Python offers many different ways to format strings, all the methods below achieve the same output.

fname = 'Bob'
lname = 'Smith'

print('My name is %s %s.' % (fname, lname))
print('My name is %(fname)s %(lname)s.' % {'fname': fname, 'lname': lname})

print('My name is {} {}.'.format(fname, lname))
print('My name is {fname} {lname}.'.format(fname=fname, lname=lname))

print(f'My name is {fname} {lname}.')

List comprehension

Used to generate lists and dictionaries with less code

numbers = [i for i in range(11)]
squares = [i**2 for i in numbers]

Lamda functions

Used to create inline functions, which is useful when no full-sized function is needed.

x = lambda a, b: a * b
print(x(4, 5))

Test if a value is above a certain threshold:

check_value = lambda x: x > 1
check_value(0.7)	#returns False
check_value(1.3)	#returns True

Assign multiple variables to the same value

Assigns all three variables a, b and c to the value 5.

a = b = c = 5

Assign values from a ordered list

All items of a list can be assigned to variables, if there are the same amount of variables.
In this example all list elements get assigned to the provided variables, from left to right, respectively.

colors = ['red', 'blue', 'green', 'yellow']
firetruck, water, flower, sun, = colors

After executing this snippet, the variables have the following values.

firetruck = 'red'
water = 'blue'
leaf = 'green'
flower = 'yellow'

Ternary conditions

Short if-else statements can be replaced with ternary conditions.

if a:
    x = 1
else:
    x = 2

= becomes
x = 1 if a else 2

args and kwargs

In Python, args and kwargs allow functions to take an unspecified amount of input values.

def print_args(*args):
    for item in args:
        print(item)

print_args(12, 'Hello World', 2.4)

def print_kwargs(**kwargs):
    for key, value in kwargs.items():
        print(key, value)

print_kwargs(id_1=10, id_2="Hello World")

Working with large numbers

When working with large numbers it can be useful to highlight every third position.

num1 = 10000000
num2 = 10_000_000   # these are the same

print(f'{num2:,}')  # 10,000,000

Looping over multiple lists at once

To loop over multiple lists with one for loop, use the zip function. It stops as soon as the shortest list is exhausted. To process all lists regardless of their length, use itertools.zip_longest().

for a, b in zip(list_a, list_b):
    print(a, b)

Unpacking values

a, b = (1, 2)               # need as many values as can be unpacked
a, b, *c = (1, 2, 3, 4)     # a = 1, b = 2, c = [3, 4]
a, *_ = (1, 2, 3)           # a = 1, throw the rest away
a, *b, c = (1, 2, 3, 4, 5)  # a = 1, b = [2, 3, 4], c = 5

Set key and value of an object

When unpacking objects, the setattr and getattr functions can come in handy.

for key, value in dict.items():
    setattr(object, key, value)

Hide user input

When user input should not be displayed (e.g. for passwords), use the getpass.getpass() function.

Abstract classes and methods

Abstract classes have the characteristic that you cannot create objects with them. In addition, abstract methods need to be implemented by the child class.
Abstract classes inherit from ABC and abstract methods need the decorator @abstractmethod.

= ABC = Abstract Base Class
from abc import ABC, abstractmethod

class parent(ABC):

    @abstractmethod
    def test_method(self):
        pass

class child(parent):
    def test_method(self, text):
        self.text = text

obj = child()
obj.test_method("HELLO")

print(test1.text)