[英]Reading data from large text file with strings and floats in Python
[英]Python defining a list of large query strings vs reading in from a file
我对在python中处理大型字符串列表时的最佳做法以及性能感到很好奇。 具体来说,我有一个包含以字符串形式包含不同postgreSQL查询的列表,我想知道有关如何初始化列表的最佳实践。 请考虑以下两种方法:
方法1-在代码中创建列表:
query_load = [("SELECT val_1, COUNT(*) as frequency "
"FROM table "
"GROUP BY val_1 "
"ORDER BY val_1 ASC"),
("SELECT val_2, COUNT(*) as frequency "
"FROM table "
"GROUP BY val_2 "
"ORDER BY val_2 ASC"),
("SELECT val_3, COUNT(*) as frequency "
"FROM table "
"GROUP BY val_3 "
"ORDER BY val_3 ASC"),
("SELECT val_4, COUNT(*) as frequency "
"FROM table "
"GROUP BY val_4 "
"ORDER BY val_4 ASC"),
...
]
方法2-将查询从文件读入列表
my_list = [line.rstrip('\n') for line in open("..Desktop/my_queries.txt")]
就可读性和更少的代码行而言,方法2似乎是更好的选择,但我希望与最佳实践保持一致。 另外,将文件逐行读入列表是否会导致性能下降(数量不菲)?
只需使用三引号引起来的字符串即可; SQL不会在意用于使您的Python源可读的空白。
query_load = [
"""
SELECT val_1, COUNT(*) as frequency
FROM table
GROUP BY val_1
ORDER BY val_1 ASC
""",
"""
SELECT val_2, COUNT(*) as frequency
FROM table
GROUP BY val_2
ORDER BY val_2 ASC
""",
# etc
]
究竟是对查询进行硬编码还是从外部文件读取查询,实际上是一个单独的问题,仅与源代码的外观有些关系。
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