即使输出在终端上正确打印，Jinja也会在输出之前在浏览器中打印出巨大的空白

Question

我的代码在我的Jinja html输出中打印了一个很大的空格。然后打印所需的结果。我正在执行一个简单的select语句，并希望显示它。我想避免（并理解为什么会这样）我的html输出中的空白。

app.py

from flask import Flask, redirect, render_template
import psycopg2
import os
import sqlalchemy

app = Flask(__name__)
app.config['SECRET_KEY'] = os.urandom(12)


@app.route('/', methods=['GET', 'POST'])
def home():
    engine = sqlalchemy.create_engine('postgresql://user:pw@localhost/db')
    result = engine.execute('select * from person.personphone limit 10;') # adventureworks db
    col_names = result.keys()
    col_vals = [dict(row) for row in result]
    ######################################### used for debugging
    for col in col_names:
        print(col, end=' ')
    print('')
    for row in col_vals:
        for col in col_names:
            print(row[col], end=' ')
        print('')
    ######################################### end debugging

    return render_template('home.html', colname=col_names, colval=col_vals)



if __name__ == '__main__':
    app.run(debug=True)

home.html

{% extends "base.html" %}

{% block content %}

Hello world

<br>

<div id="table">
    <table>
        <tr>
        {% for col in colname %}
            <th>{{ col }} </th>
        {% endfor %}
        </tr>
        <br>
        {% for row in colval %}
            <tr>
            {% for col in colname %}
                <td>{{ row[col] }} </td>
            {% endfor %}
            </tr>
            <br>
        {% endfor %}
    </table>
</div>

{% endblock %}

端子输出：

Jinja在浏览器上的输出：

Answer 1

在表格行之间有<br>标签，这些标签被打印在表格上方。删除它们-它们不应在那里：

<div id="table">
    <table>
        <tr>
        {% for col in colname %}
            <th>{{ col }} </th>
        {% endfor %}
        </tr>
        {% for row in colval %}
            <tr>
            {% for col in colname %}
                <td>{{ row[col] }} </td>
            {% endfor %}
            </tr>
        {% endfor %}
    </table>
</div>