列表解析式生成字典

場景：

看Python資料時學到了一種通過列表解析式生成字典的方式，工作暫未用到過，先記錄下來。

程式碼：

# 從 Python 2.7 開始，甚至可以用解析式生成字典（雜湊表）
# Taken from page 70 chapter 3 of Fluent Python by Luciano Ramalho
# 有如下列表，元素為多個tuple。
In [8]: DIAL_CODES = [
   ...:     (86, 'China'),
   ...:     (91, 'India'),
   ...:     (1, 'United States'),
   ...:     (62, 'Indonesia'),
   ...:     (55, 'Brazil'),
   ...:     (92, 'Pakistan'),
   ...:     (880, 'Bangladesh'),
   ...:     (234, 'Nigeria'),
   ...:     (7, 'Russia'),
   ...:     (81, 'Japan'),
   ...:     ]
   ...:


# 通過列表解析式生成字典
In [9]: country_code = {country: code for code, country in DIAL_CODES}

# 輸出字典
In [10]: country_code
Out[10]:
{'China': 86,
 'India': 91,
 'United States': 1,
 'Indonesia': 62,
 'Brazil': 55,
 'Pakistan': 92,
 'Bangladesh': 880,
 'Nigeria': 234,
 'Russia': 7,
 'Japan': 81}

# 還可以過濾條件生成字典
In [11]: {code: country.upper() for country, code in country_code.items() if code < 66}
Out[11]: {1: 'UNITED STATES', 62: 'INDONESIA', 55: 'BRAZIL', 7: 'RUSSIA'}