Author Archives: Dávid

How to run python code from Windows console

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I am quite new to python programming but happy to use it for quick test cases like API calls or file operations. To run these scenarios I run them in different ways:

From file

One of the easiest way to call your script is to store them in a file and make python run them:

print('I am run from a file!')

content of run-me.py

Run it from command line:

python run-me.py

From inline command line

If you don’t want to save your code to a file, you can run it from inline:

python -c "print('I am from inline command line')"

From inline command line, multi line

Normally python code is segmented by new lines and indentation, but inline we can separate commands by semicolons:

SQLite returning value when deleting

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Imagine the scenario when you have an SQLite database and you need to delete some of it’s content based on conditions, then list the IDs what you just deleted.

Normally it would take at least two queries: first select the ids based on the condition, store them in a list, then delete the rows with the just queried ids and continue to work with them.

SQLite has a “RETURNING” keyword, which can come in handy to reduce the queries run to just one.

For example we can utilize it as following:

DELETE FROM [file] WHERE toDelete == 1 RETURNING name

The above code will remove the rows marked “toDelete” and return the name-s of those.

Quick example using python 3:

import sqlite3

con = sqlite3.connect('./test.db')
cur = con.cursor()
cur.execute('CREATE TABLE [file] (id, name, toDelete)')
cur.execute('INSERT INTO [file] (id, name, toDelete) VALUES (1, "testFile1", 0)')
cur.execute('INSERT INTO [file] (id, name, toDelete) VALUES (2, "testFile2", 0)')
cur.execute('INSERT INTO [file] (id, name, toDelete) VALUES (3, "testFile3", 1)')
cur.execute('INSERT INTO [file] (id, name, toDelete) VALUES (4, "testFile4", 1)')   

print(cur.execute('DELETE FROM [file] WHERE toDelete == 1 RETURNING name').fetchall())

con.commit()
con.close()

It will print the following:

[('testFile3',), ('testFile4',)]