I would like someone to help me with an excerpt of this SQL and Python code

Question

I’m trying to capture a flag of the site Hacker101 CFT and I came across a code snippet.

IN THAT SPECIFIC PART:

 if cur.execute('SELECT password FROM admins WHERE username=\'%s\'' % request.form['username'].replace('%', '%%')) == 0:

would like to know the meaning of these symbols ( '%s '' %) in the language, after the word username, I intend to study this part to understand the code completely but do not know which keyword to use to search on these ( '%s' %) symbols.

// TRECHO DA MENSAGEM DE ERRO COMPLETO

Traceback (most recent call last):
  File "./main.py", line 145, in do_login
    if cur.execute('SELECT password FROM admins WHERE username=\'%s\'' % request.form['username'].replace('%', '%%')) == 0:
  File "/usr/local/lib/python2.7/site-packages/MySQLdb/cursors.py", line 255, in execute
    self.errorhandler(self, exc, value)
  File "/usr/local/lib/python2.7/site-packages/MySQLdb/connections.py", line 50, in defaulterrorhandler
    raise errorvalue
ProgrammingError: (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ''''' at line 1")

Answer 1

This %s is from the Python String Format, serves for you to format strings, see the example below.

name = "Mundo"
print("Olá  %s!" %name)

The output of the command below is:

Olá Mundo!

The %s is used when vc will replace with a string, it also has the %d for when it is a numeral.
You can see more about string format here.