[英]For Loop or executemany - Python and SQLite3
I have started to learn Python and SQL recently and have a question. 我最近开始学习Python和SQL并且有一个问题。
Using Python with SQLite3 I have written the following code: 使用Python和SQLite3我编写了以下代码:
# Use sqlite3 in the file
import sqlite3
# Create people.db if it doesn't exist or connect to it if it does exist
with sqlite3.connect("people.db") as connection:
c = connection.cursor()
# Create new table called people
c.execute("""CREATE TABLE IF NOT EXISTS people(firstname TEXT, lastname TEXT, age INT, occupation TEXT)""")
people_list = [
('Simon', 'Doe', 20, 'Python Master'),
('John', 'Doe', 50, 'Java Master'),
('Jane', 'Doe', 30, 'C++ Master'),
('Smelly', 'Doe', 2, 'Shower Master')
]
# Insert dummy data into the table
c.executemany("""INSERT INTO people(firstname, lastname, age, occupation) VALUES(?, ?, ?, ?)""", people_list)
I noticed that I can do the same thing using a for loop instead of executemany like so: 我注意到我可以使用for循环而不是executemany来执行相同的操作:
# Use sqlite3 in the file
import sqlite3
# Create people.db if it doesn't exist or connect to it if it does exist
with sqlite3.connect("people.db") as connection:
c = connection.cursor()
# Create new table called people
c.execute("""CREATE TABLE IF NOT EXISTS people(firstname TEXT, lastname TEXT, age INT, occupation TEXT)""")
people_list = [
('Simon', 'Doe', 20, 'Python Master'),
('John', 'Doe', 50, 'Java Master'),
('Jane', 'Doe', 30, 'C++ Master'),
('Smelly', 'Doe', 2, 'Shower Master')
]
# Insert dummy data into the table
for person in people_list:
c.execute("""INSERT INTO people(firstname, lastname, age, occupation) VALUES(?, ?, ?, ?)""", person)
I'm just wondering which one is more efficient and used more often? 我只是想知道哪一个更有效率并且更频繁地使用?
A batch insert with executemany
will be more efficient, and the performance difference will typically be quite large as your number of records gets large. 使用
executemany
的批量插入将更有效,并且随着记录数量的增加,性能差异通常会非常大。 There is a significant overhead to executing an insert statement, which you incur over and over again if you insert one row at a time. 执行insert语句会产生很大的开销,如果一次插入一行,就会反复出现这种情况。
You should prefer a batch insert whenever it is straightforward to do so. 只要直接插入,您就应该更喜欢批量插入。
In some cases, it may be much simpler to code an algorithm that inserts one row at a time. 在某些情况下,编写一次插入一行的算法可能要简单得多。 For example, if you are receiving data from somewhere one item at a time, it may be simpler to just insert it as you get it, rather than building up a list and doing a single insert when you have saved up a lot of data.
例如,如果您一次从某个项目的某个位置接收数据,则可能更容易在您获取数据时插入数据,而不是在保存大量数据时构建列表并执行单个插入。 In such a case, you need to consider the tradeoffs between performance and simplicity of code.
在这种情况下,您需要考虑性能和代码简单性之间的权衡。 It's often better to start off with the simple approach (insert one row at a time) and then only optimize to something else if you find it's not performant.
通常最好从简单的方法开始(一次插入一行),然后如果发现它不具备性能,则只优化其他方法。
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