The Zen Of Python (Pythonic Style Coding)

2023-11-25

筆記 Pythonic Style Coding，藉由風格對比的方式，深化至自己的心中。

說明

1. Using List Comprehension

• Unpythonic 😥

numbers = [1, 2, 3, 4, 5]
squares = []
for n in numbers:
    squares.append(n ** 2)

• Pythonic 😎

numbers = [1, 2, 3, 4, 5]
squares = [n ** 2 for n in numbers]

---

2. Iterating Over Dictionary Items

• Unpythonic 😥

dictionary = {'a': 1, 'b': 2, 'c': 3}
for key in dictionary.keys():
    print(key, dictionary[key])

• Pythonic 😎

dictionary = {'a': 1, 'b': 2, 'c': 3}
for key, value in dictionary.items():
    print(key, value)

---

3. File Operations : with

• Unpythonic 😥

file = open('file.txt', 'r')
content = file.read()
print(content)
file.close()

• Pythonic 😎

with open('file.txt', 'r') as file:
    content = file.read()
    print(content)

---

4. Swapping Variable Values

• Unpythonic 😥

a = 1
b = 2
temp = a
a = b
b = temp

• Pythonic 😎

a = 1
b = 2
a, b = b, a

---

5. Conditional Expressions

• Unpythonic 😥

if condition:
    x = 1
else:
    x = 0

• Pythonic 😎

x = 1 if condition else 0

---

6. 使用 enumerate (Using enumerate)

• Unpythonic 😥

my_list = ['apple', 'banana', 'grape']
i = 0
for item in my_list:
    print(i, item)
    i += 1

• Pythonic 😎

my_list = ['apple', 'banana', 'grape']
for i, item in enumerate(my_list):
    print(i, item)

---

7. Using the Zip Function

• Unpythonic 😥

keys = ['a', 'b', 'c']
values = [1, 2, 3]
my_dict = {}
for i in range(len(keys)):
    my_dict[keys[i]] = values[i]

• Pythonic 😎

keys = ['a', 'b', 'c']
values = [1, 2, 3]
my_dict = dict(zip(keys, values))

---

8. Defining Default Values in Functions

• Unpythonic 😥

def foo(bar):
    if bar is None:
        bar = []
    # do something with bar

• Pythonic 😎

def foo(bar = None):
    bar = bar or []
    # do something with bar

---

9. Using Generator Expressions

• Unpythonic 😥

numbers = [1, 2, 3, 4, 5]
sum_squares = sum([n ** 2 for n in numbers])

• Pythonic 😎

numbers = [1, 2, 3, 4, 5]
sum_squares = sum(n ** 2 for n in numbers)

---

10. Using *args and **kwargs

• Unpythonic 😥

def foo(a, b, c, d):
    print(a, b, c, d)
foo(1, 2, 3, 4)

• Pythonic 😎

def foo(*args, **kwargs):
    print(*args, **kwargs)
foo(1, 2, c=3, d=4)

---

11. String Concatenation

• Unpythonic 😥

strings = ['Hello', 'World']
result = ''
for s in strings:
    result += s

• Pythonic 😎

strings = ['Hello', 'World']
result = ''.join(strings)

---

12. Filtering Lists with Comprehension

• Unpythonic 😥

numbers = [1, 2, 3, 4, 5, 6]
even = []
for n in numbers:
    if n % 2 == 0:
        even.append(n)

• Pythonic 😎

numbers = [1, 2, 3, 4, 5, 6]
even = [n for n in numbers if n % 2 == 0]

---

13. Multiple Return Values

• Unpythonic 😥

def get_user():
    # ... some logic ...
    return name, age, email
result = get_user()
name = result[0]
age = result[1]
email = result[2]

• Pythonic 😎

def get_user():
    # ... some logic ...
    return name, age, email
name, age, email = get_user()

---

14. sing List's extend Method

• Unpythonic 😥

list1 = [1, 2, 3]
list2 = [4, 5, 6]
for item in list2:
    list1.append(item)

• Pythonic 😎

list1 = [1, 2, 3]
list2 = [4, 5, 6]
list1.extend(list2)

---

15. 字典預設值 (Dictionary Default Values)

• Unpythonic 😥

dict = {'a': 1, 'b': 2}
if 'c' in dict:
    value = dict['c']
else:
    value = 'default'

• Pythonic 😎

dict = {'a': 1, 'b': 2}
value = dict.get('c', 'default')

---

16. List Slicing

• Unpythonic 😥

my_list = [1, 2, 3, 4, 5]
first_three = []
for i in range(3):
    first_three.append(my_list[i])

• Pythonic 😎

my_list = [1, 2, 3, 4, 5]
first_three = my_list[:3]

---

17. Using map and filter

• Unpythonic 😥

numbers = [1, 2, 3, 4, 5]
squares = []
for n in numbers:
    squares.append(n ** 2)
even_squares = []
for square in squares:
    if square % 2 == 0:
        even_squares.append(square)

• Pythonic 😎

numbers = [1, 2, 3, 4, 5]
even_squares = map(lambda n: n ** 2, filter(lambda n: n % 2 == 0, numbers))

---

18. Using all or any

• Unpythonic 😥

values = [True, True, False]
all_true = True
for v in values:
    if not v:
        all_true = False
        break

• Pythonic 😎

values = [True, True, False]
all_true = all(values)

---

19. Using Sets to Remove Duplicates

• Unpythonic 😥

my_list = [1, 2, 2, 3, 3, 3]
unique_list = []
for item in my_list:
    if item not in unique_list:
        unique_list.append(item)

• Pythonic 😎

my_list = [1, 2, 2, 3, 3, 3]
unique_list = list(set(my_list))

---

20. Concise Function Definition

• Unpythonic 😥

def square(x):
    return x * x

• Pythonic 😎

square = lambda x: x * x

---

21. Merging Dictionaries

• Unpythonic 😥

dict1 = {'a': 1, 'b': 2}
dict2 = {'b': 3, 'c': 4}
merged = dict1.copy()
for key in dict2:
    merged[key] = dict2[key]

• Pythonic 😎

dict1 = {'a': 1, 'b': 2}
dict2 = {'b': 3, 'c': 4}
merged = {**dict1, **dict2}

---

22. Reversing Lists

• Unpythonic 😥

my_list = [1, 2, 3, 4, 5]
reversed_list = []
for item in reversed(my_list):
    reversed_list.append(item)

• Pythonic 😎

my_list = [1, 2, 3, 4, 5]
reversed_list = my_list[::-1]

---

23. Set Operations

• Unpythonic 😥

set1 = {1, 2, 3}
set2 = {3, 4, 5}
intersection = set()
for item in set1:
    if item in set2:
        intersection.add(item)

• Pythonic 😎

set1 = {1, 2, 3}
set2 = {3, 4, 5}
intersection = set1 & set2

同場加映 🎬

union = set1 | set2

difference = set1 - set2

symmetric_difference = set1 ^ set2

is_subset = set1 <= set2

is_superset = set1 >= set2

is_disjoint = set1.isdisjoint(set2)

---

24. 使用 defaultdict (Using defaultdict)

• Unpythonic 😥

my_dict = {}
for key, value in pairs:
    if key not in my_dict:
        my_dict[key] = []
    my_dict[key].append(value)

• Pythonic 😎

from collections import defaultdict
my_dict = defaultdict(list)
for key, value in pairs:
    my_dict[key].append(value)

---

25. Logging Function Execution Time

• Unpythonic 😥

import time

def my_function():
    start_time = time.time()
    # function logic
    end_time = time.time()
    print(f"Time taken: {end_time - start_time} seconds")

• Pythonic 😎

import time
import functools

def timer(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        start_time = time.time()
        value = func(*args, **kwargs)
        end_time = time.time()
        print(f"{func.__name__} took {end_time - start_time} seconds")
        return value
    return wrapper

@timer
def my_function():
    # function logic

---

26. 鏈式比較 (Chained Comparisons)

• Unpythonic 😥

if x > 5 and x < 10:
    pass

• Pythonic 😎

if 5 < x < 10:
    pass

---

27. 使用 reversed 函数 (Using reversed)

• Unpythonic 😥

for i in range(len(my_list) - 1, -1, -1):
    print(my_list[i])

• Pythonic 😎

for item in reversed(my_list):
    print(item)

---

28. 字典推導式(Dictionary Comprehension)

• Unpythonic 😥

keys = ['a', 'b', 'c']
values = [1, 2, 3]
my_dict = {}
for i in range(len(keys)):
    my_dict[keys[i]] = values[i]

• Pythonic 😎

keys = ['a', 'b', 'c']
values = [1, 2, 3]
my_dict = {k: v for k, v in zip(keys, values)}

---

29. 同時獲取索引和值(Getting Index and Value Simultaneously)

• Unpythonic 😥

my_list = ['a', 'b', 'c']
for i in range(len(my_list)):
    print(i, my_list[i])

• Pythonic 😎

my_list = ['a', 'b', 'c']
for index, value in enumerate(my_list):
    print(index, value)

---

30. 使用生成器表達式(Using Generator Expressions)

• Unpythonic 😥

def square_numbers(nums):
    for num in nums:
        yield num * num

• Pythonic 😎

nums = [1, 2, 3, 4]
square_gen = (num * num for num in nums)

---

31. 函數參數解包 (Function Parameter Unpacking)

• Unpythonic 😥

def my_func(a, b, c):
    print(a, b, c)

args = [1, 2, 3]
my_func(args[0], args[1], args[2])

• Pythonic 😎

args = [1, 2, 3]
my_func(*args)

---

32. 使用 itertools.chain 合并迭代器 (Using itertools.chain)

• Unpythonic 😥

list1 = [1, 2, 3]
list2 = [4, 5, 6]
for list in (list1, list2):
    for item in list:
        process(item)

• Pythonic 😎

import itertools
list1 = [1, 2, 3]
list2 = [4, 5, 6]
for item in itertools.chain(list1, list2):
    process(item)

33. 使用 _ 忽略特定值 (Using _ to Ignore Specific Values)

• Unpythonic 😥

a, b, c = (1, 2, 3)
print(a, b)

• Pythonic 😎

a, b, _ = (1, 2, 3)
print(a, b)

---

34. 使用 := 賦值表達式（自 Python 3.8 起） (Using := Assignment Expression)

• Unpythonic 😥

n = len(my_list)
if n > 4:
    print(f"List is too long ({n} elements, expected <= 4)")

• Pythonic 😎

if (n := len(my_list)) > 4:
    print(f"List is too long ({n} elements, expected <= 4)")

---

35. 使用 pathlib 處理路徑 (Using pathlib for Path Handling)

• Unpythonic 😥

import os
filepath = os.path.join('dir', 'file.txt')

• 語法糖寫法（使用 pathlib）：

from pathlib import Path
filepath = Path('dir') / 'file.txt'

---

36. 使用 or 簡化賦值 (Simplifying Assignment with or)

• Unpythonic 😥

name = ''
if user_name:
    name = user_name
else:
    name = 'Guest'

• Pythonic 😎

name = user_name or 'Guest'

---

37. Using Set Comprehension

• Unpythonic 😥

my_list = [1, 2, 2, 3, 3, 3]
my_set = set()
for item in my_list:
    my_set.add(item)

• Pythonic 😎

my_list = [1, 2, 2, 3, 3, 3]
my_set = {item for item in my_list}

---

38. Using f-string

• Unpythonic 😥

name = "Alice"
greeting = "Hello, " + name + "!"

• Pythonic 😎

name = "Alice"
greeting = f"Hello, {name}!"

---

39. 以優雅方式進行異常處理 (Concise Exception Handling)

• Unpythonic 😥

try:
    result = 10 / number
except ZeroDivisionError:
    result = "Infinity"

• Pythonic 😎

result = 10 / number if number else "Infinity"

---

40. 使用 itertools (Using itertools)

• Unpythonic 😥

pairs = []
for a in range(3):
    for b in range(3):
        if a != b:
            pairs.append((a, b))

• Pythonic 😎

import itertools
pairs = [(a, b) for a, b in itertools.permutations(range(3), 2)]

---

41. 使用 functools.reduce (Using functools.reduce)

• Unpythonic 😥

numbers = [1, 2, 3, 4]
result = 0
for num in numbers:
    result += num

• Pythonic 😎

from functools import reduce
numbers = [1, 2, 3, 4]
result = reduce(lambda x, y: x + y, numbers)

---

42. 使用 next 與迭代器 (Using next with Iterators)

• Unpythonic 😥

for item in my_iterable:
    first_item = item
    break

• Pythonic 😎

first_item = next(iter(my_iterable))

---

43. Using List's pop

• Unpythonic 😥

last_item = my_list[len(my_list) - 1]
my_list = my_list[:-1]

• Pythonic 😎

last_item = my_list.pop()

---

44. 迴圈中使用 else (Using else in Loops)

• Unpythonic 😥

found = False
for item in my_list:
    if condition(item):
        process(item)
        found = True
        break
if not found:
    handle_not_found()

• Pythonic 😎

for item in my_list:
    if condition(item):
        process(item)
        break
else:
    handle_not_found()

---

45. 使用 contextlib.suppress (Using contextlib.suppress)

• Unpythonic 😥

try:
    os.remove(filename)
except FileNotFoundError:
    pass

• Pythonic 😎

from contextlib import suppress
with suppress(FileNotFoundError):
    os.remove(filename)

---

46. Optimizing Code with Assignment Expressions

• Unpythonic 😥

file = open('test.txt')
data = file.readline()
while data:
    process(data)
    data = file.readline()

• Pythonic 😎

with open('test.txt') as file:
    while (data := file.readline()):
        process(data)

---

47. Using List's clear Method

• Unpythonic 😥

my_list = [1, 2, 3, 4, 5]
del my_list[:]

• Pythonic 😎

my_list = [1, 2, 3, 4, 5]
my_list.clear()

---

48. Using zip to Iterate Over Multiple Sequences Simultaneously

• Unpythonic 😥

list1 = [1, 2, 3]
list2 = ['a', 'b', 'c']
for i in range(len(list1)):
    print(list1[i], list2[i])

• Pythonic 😎

list1 = [1, 2, 3]
list2 = ['a', 'b', 'c']
for number, letter in zip(list1, list2):
    print(number, letter)

---

49. 使用 divmod 函數 (Using divmod Function)

• Unpythonic 😥

dividend, divisor = 20, 7
quotient = dividend // divisor
remainder = dividend % divisor

• Pythonic 😎

dividend, divisor = 20, 7
quotient, remainder = divmod(dividend, divisor)

---

50. 條件判斷 (Optimizing Conditional Statements)

• Unpythonic 😥

if x == 'a' or x == 'b' or x == 'c':
    pass

• Pythonic 😎

if x in ('a', 'b', 'c'):
    pass

---

51. 多重賦值 (Optimizing Multiple Assignments)

• Unpythonic 😥

x = 5
y = 5
z = 5

• Pythonic 😎

x = y = z = 5

---

52. Membership Check with in

• Unpythonic 😥

if my_list.count(x) > 0:
    pass

• Pythonic 😎

if x in my_list:
    pass

---

53. Using collections.Counter for Element Counting

• Unpythonic 😥

my_list = ['a', 'b', 'c', 'a', 'b', 'b']
count = {}
for item in my_list:
    if item in count:
        count[item] += 1
    else:
        count[item] = 1

• Pythonic 😎

from collections import Counter
my_list = ['a', 'b', 'c', 'a', 'b', 'b']
count = Counter(my_list)