title: Why can't replace placeholder with format function in pymysql?
body: <p>How i create the table <code>mingyan</code>.</p>
  
  <pre><code>CREATE TABLE `mingyan` (
    `tag` varchar(10) DEFAULT NULL,
    `cont` varchar(255) DEFAULT NULL
  ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
  </code></pre>
  
  <p>It's said that string format function with <code>{}</code> is more pythonic way than  placeholder <code>%</code>.<br>
  In my scrapy to write some fields into a table <code>mingyan</code>.</p>
  
  <pre><code>self.cursor.execute("insert into mingyan(tag, cont) values (%s, %s)",(item['tag'],item['cont']))
  </code></pre>
  
  <p>It works fine in my scrapy,now i replace the placeholder way with string format function.</p>
  
  <pre><code>self.cursor.execute("insert into mingyan(tag, cont) values ({},{})".format(item['tag'],item['cont']))
  </code></pre>
  
  <p>The scrapy  got error info </p>
  
  <pre><code>pymysql.err.ProgrammingError: (1064, "You have an error in your SQL syntax; 
  </code></pre>
  
  <p>Why can't replace placeholder with format function in pymysql?</p>
  
  <p>The item in scrapy doucment.<br>
  <a href="https://docs.scrapy.org/en/latest/topics/items.html?highlight=item#item-fields" rel="nofollow noreferrer">item meaning in scrapy</a></p>