Python-Programming-Idioms.md

Python Programming Idioms

The word "idiom" refers to a habitual practice, a conventional approach, or a customary way of doing things. Since Python differs significantly from many other programming languages in both syntax and usage, a Python developer who fails to master these idioms will not be able to write "Pythonic" code. Below, we summarize some idiomatic code patterns commonly used in Python development.

1. Make code both importable and executable.

   if __name__ == '__main__':

2. Use the following approach to check for logical "true" or "false".

   if x:
   if not x:

   Good code:

   name = 'jackfrued'
   fruits = ['apple', 'orange', 'grape']
   owners = {'1001': 'Luo Hao', '1002': 'Wang Dachui'}
   if name and fruits and owners:
       print('I love fruits!')

   Bad code:

   name = 'jackfrued'
   fruits = ['apple', 'orange', 'grape']
   owners = {'1001': 'Luo Hao', '1002': 'Wang Dachui'}
   if name != '' and len(fruits) > 0 and owners != {}:
       print('I love fruits!')

3. Make good use of the in operator.

   if x in items: # containment check
   for x in items: # iteration

   Good code:

   name = 'Hao LUO'
   if 'L' in name:
       print('The name has an L in it.')

   Bad code:

   name = 'Hao LUO'
   if name.find('L') != -1:
       print('This name has an L in it!')

4. Swap two values without using a temporary variable.

   a, b = b, a

5. Build strings from sequences.

   Good code:

   chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd']
   name = ''.join(chars)
   print(name)  # jackfrued

   Bad code:

   chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd']
   name = ''
   for char in chars:
       name += char
   print(name)  # jackfrued

6. EAFP is better than LBYL.

   EAFP - Easier to Ask Forgiveness than Permission.

   LBYL - Look Before You Leap.

   Good code:

   d = {'x': '5'}
   try:
       value = int(d['x'])
       print(value)
   except (KeyError, TypeError, ValueError):
       value = None

   Bad code:

   d = {'x': '5'}
   if 'x' in d and isinstance(d['x'], str) \
   		and d['x'].isdigit():
       value = int(d['x'])
       print(value)
   else:
       value = None

7. Use enumerate for iteration.

   Good code:

   fruits = ['orange', 'grape', 'pitaya', 'blueberry']
   for index, fruit in enumerate(fruits):
   	print(index, ':', fruit)

   Bad code:

   fruits = ['orange', 'grape', 'pitaya', 'blueberry']
   index = 0
   for fruit in fruits:
       print(index, ':', fruit)
       index += 1

8. Use comprehensions to generate lists.

   Good code:

   data = [7, 20, 3, 15, 11]
   result = [num * 3 for num in data if num > 10]
   print(result)  # [60, 45, 33]

   Bad code:

   data = [7, 20, 3, 15, 11]
   result = []
   for i in data:
       if i > 10:
           result.append(i * 3)
   print(result)  # [60, 45, 33]

9. Use zip to combine keys and values to create a dictionary.

   Good code:

   keys = ['1001', '1002', '1003']
   values = ['Luo Hao', 'Wang Dachui', 'Bai Yuanfang']
   d = dict(zip(keys, values))
   print(d)

   Bad code:

   keys = ['1001', '1002', '1003']
   values = ['Luo Hao', 'Wang Dachui', 'Bai Yuanfang']
   d = {}
   for i, key in enumerate(keys):
       d[key] = values[i]
   print(d)

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