Flask 分页：UnboundLocalError：在赋值错误之前引用了局部变量“res”

Question

I'm working on the flask pagination, when i try to achieve it, i get the UnboundLocalError, if i try to remove all the variables, still the pagination doesn't work.

@app.route('/')
def index():
    cur = mysql.connection.cursor(MySQLdb.cursors.DictCursor) 
    return render_template('index.html')

@app.route("/fetchrecords",methods=["POST","GET"])
def fetchrecords():
    per_page = 10
    page = request.args.get(get_page_parameter(), type=int, default=1)
    offset = (page - 1) * per_page
    cur = mysql.connection.cursor(MySQLdb.cursors.DictCursor)
    if request.method == 'POST':
         query = request.form['query']
         cur.execute("SELECT * FROM emp ORDER BY pid")
         res = cur.fetchall()
         for i in res:
             total +=float(i['salary'])
         numrows = int(cur.rowcount)             
         cur.execute("SELECT * FROM emp ORDER BY pid DESC LIMIT %s, %s", (per_page, offset))
         res = cur.fetchall()
         if query == '':
             cur.execute("SELECT * FROM emp ORDER BY pid")
             total = cur.fetchall() 
             numrows = int(cur.rowcount)      
             cur.execute("SELECT * FROM emp ORDER BY pid DESC LIMIT %s, %s", (per_page, offset))
             res = cur.fetchall()     
             pagination = Pagination(page=page, per_page=per_page, offset=offset, total=len(total))                                           
        else:
              search_text = request.form['query']
              cur.execute("SELECT * from emp WHERE name LIKE '%{}%' OR title LIKE '%{}%' OR pid LIKE '%{}%' ORDER BY pid".format(search_text,search_text,search_text))
              res = cur.fetchall() 
              for i in res: 
                  total +=float(i['salary'])
              numrows = int(cur.rowcount) 
              pagination = Pagination(page=page, per_page=per_page, offset=offset, total=len(total), record_name='res')
  elif request.method == 'GET':
        cur.execute("SELECT * FROM emp ORDER BY pid")
        total = cur.fetchall()
        per_page = 25 
        page = request.args.get(get_page_parameter(), type=int, default=1)      
        offset = (page - 1) * per_page
        pagination = Pagination(page=page, per_page=per_page,total=len(total), 
              css_framework='bootstrap4')   
        numrows = int(cur.rowcount)
        cur.execute("SELECT * FROM portal ORDER BY pid DESC LIMIT %s, %s", (per_page, offset))
        res = cur.fetchall()    
             
  return jsonify({'htmlresponse': render_template('response.html', res=res, numrows=numrows, total=total,pagination=pagination)})

resonse.html

<h4>Total : {{numrows}} </h4></tr>
<table class="table table-striped table-bordered">
    <thead>
        <tr>
          ..Table header.. 
        </tr>
    </thead>
    {% for row in res %}  
    <tr>  Data base values here...</tr>
    {% endfor %}
</table>
{{pagination.links}}

Can anyone please help me, how to work with pagination and whats wrong I'm doing. This would be very helpful thanks in advance

Answer 1

It happens when the endpoint is invoked via an http get request. The creation of the res variable is enclosed within this if:

if request.method == 'POST':

while this return here (which refers to the variable res ) is outside the if

return jsonify({'htmlresponse': render_template('response.html', res=res, numrows=numrows, total=total,pagination=pagination)})