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The Zen of Python - Developer Guidelines

PEP 20 (a.k.a. The Zen of Python)

The Zen of Python, by Tim Peters

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
 If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!

The Zen of Python is available in Python via

import this

Guideline 1

1. Beautiful is better than ugly

Example 1

Bad

from first_module.second_module.third_module import \
    long_name_function_1, \
    long_name_function_2, \
    long_name_function_3

Good

from first_module.second_module.third_module import
(
    long_name_function_1,
    long_name_function_2,
    long_name_function_3
)

Example 2

Bad

message = "This is very very very long message, you should think about splitting " \
          "this message into multiple lines of code for better readability"

Good

message = (
    "This is very very very long message, you should think about splitting"
    " this message into multiple lines of code for better readability"
)

Guideline 2

2. Explicit is better than implicit

Example 1

Bad

def make_dict(*args):
    x, y = args
    return dict(**locals())

Good

def make_dict(x, y):
   return {'x': x, 'y': y}

Example 2

Bad

from math import sin

def sin(x):
   return 'It's a sin'
   
print(sin(180))

Good

import math

def sin(x):
    return 'It's a sin'
    
print(sin(180))
print(math.sin(180))

Guideline 3

3. Simple is better than complex
4. Complex is better than complicated

Guideline 4

5. Flat is better than nested

Bad

if condition_1:
    if condition_2:
        # Do something
    else:
        return
else:
    return

Good

if not condition_1:
    return
if not condition_2:
    return
# Do something

Guideline 5

6. Sparse is better than dense

Bad

# Example 1
print('Hello'); print('World')

# Example 2
if is_authenticated: print('You are authenticated')

# Example 3
if <complex condition 1> and <complex condition 2> and <complex condition 3>:
    # Do something

Good

# Example 1
print('Hello')
print('World')

# Example 2
if is_authenticated:
    print('You are authenticated')

# Example 3
condition_1 = <complex condition 1>
condition_2 = <complex condition 2>
condition_3 = <complex condition 3>
if condition_1 and condition_2 and condition_3:
    # Do something

Guideline 6

7. Readability counts.
8. Special cases aren't special enough to break the rules.
9. Although practicality beats purity.

Guideline 7

10. Errors should never pass silently. 
11. Unless explicitly silenced.

Bad

try:
    # Do something with possible exceptions
except:
    pass
  • The except clause without any specified exception will catch everything and ignore it.
  • A broad except clause can hide bugs and leave them to cause some problem later on

Good

try:
    # Do something with possible exceptions
except:
    print('An exception happend')
    raise
  • Always explicitly identify the exceptions you will catch by name and handle only those exceptions
  • You can simply log the exceptions or otherwise acknowledge the exception and re-raise it

Guideline 8

12. In the face of ambiguity, refuse the temptation to guess.

Guideline 9

13. There should be one-- and preferably only one --obvious way to do it.
14. Although that way may not be obvious at first unless you're Dutch.

Example 1

# There are 3 ways to do string formatting, but follow one style in your codebase is recommended
programming_language = 'Python'

# Method 1
print('The Zen of %s' % programming_language)

# Method 2
print('The Zen of {}'.format(programming_language))

# Method 3
print(f'The Zen of {programming_lanaguage}')

Example 2

# There are 2 conventions for string types, either single/double quotation marks, but you should pick one throught the code base
programming_language_1 = 'Python'
programming_language_2 = "Python"

In case there are multiple ways to solve a problem in Python, then developer needs to be familiar with all of the different methods. However, developers should follow the same choice throught the code base for better readibility

Guideline 10

15. Now is better than never.
16. Although never is often better than *right* now.
17. If the implementation is hard to explain, it's a bad idea.
18. If the implementation is easy to explain, it may be a good idea.
19. Namespaces are one honking great idea -- let's do more of those!

References

  1. https://peps.python.org/pep-0020/
  2. The Hitchhiker's Guide to Python, Kenneth Reitz & Tanya Schlusser
  3. https://initialcommit.com/blog/zen-of-python
  4. https://betterprogramming.pub/contemplating-the-zen-of-python-186722b833e5