• 使用enumerate，不要用range(len(x))

city_list = ["Taipei","beijing","wuhan"]
for i in range(len(city_list)):
    print('%s: %s' %(i, city_list[i]))

city_list = ["Taipei","beijing","wuhan"]
for idx, city in enumerate(city_list):
    print('%s: %s' %(idx, city))

相同的結果但是enumerate函數寫法更加簡潔，且有更高的閱讀性。

• 使用List Comprehensions，不要用 for raw loop
  List Comprehension 例子是將一個 List 轉換成另外一個 List。

#Before
squares = []
for i in range(10):
     squares.append(i*i)
print(squares)
# After
squares = [i*i for i in range(10)]
print(squares)

• 使用generator來節省記憶體
  當需要迭代較大的串列時候會消耗掉大量記憶體。因此建議使用generator來節省記憶體。如下範例

# save memory by generator
import sys

my_list = [i for i in range(100000)]
print(type(my_list))
print(sys.getsizeof(my_list), "bytes")

my_gen =(i for i in range(100000))
print(type(my_gen))
print(sys.getsizeof(my_gen), "bytes")

• Python字典使用.get()來設定預設值
  get(key) 方法在 key值不在字典中時，可以返回預設值Non 或者設置的預設值。如果dict[key] 在 key不在字典中时，會造成KeyError 異常。

test_dict = {"name": "Wendy"}
name = test_dict.get("age")
print(name)

test_dict = {"name": "Wendy"}
name = test_dict.get("age", 0)
print(name)

test_dict = {"name": "Wendy", "age": 23}
name = test_dict.get("age", 0)
print(name)

• 使用collections.counter做字典中元素出現次數統計

from collections import Counter
my_list = [10,10,10,3,4,4,5,5,5,5]
counter = Counter(my_list)
print(counter)

• 字串串接使用.join()
  可使用for迴圈迭代並串接上來，但是此方法效能較差

list_of_strings = ["Hello", "my", "name", "is", "Wendy"]
my_string = ""
for s in list_of_strings:
    my_string += s + " "
print(my_string)
建議使用.join()做字串串串接
list_of_strings = ["Hello", "my", "name", "is", "Wendy"]
my_string = " ".join(list_of_strings)
print(my_string)