提交表单后，字段值似乎被设置回空。我正在做一些表单验证；如果表单无效，我将让它显示错误列表中的错误消息，但我希望保留字段值。有没有办法做到这一点？
这是我验证表单的观点：
@app.route('/booking', methods=['GET', 'POST'])
def booking():
errors = []
if request.method == 'GET':
return render_template('booking.html', errors=errors)
else:
# grab values from form fields and store them in objects
start_date = request.form['start_date']
end_date = request.form['end_date']
name = request.form['name'].strip()
email = request.form['email'].strip()
# check if all fields are non-empty and raise an error if not
if not start_date or not end_date or not name or not email:
errors.append('Please enter all the fields.')
else:
# converts dates to Unix time-stamp for easier validation/calculations
start_timestamp = dt.strptime(start_date, "%d/%m/%Y")
end_timestamp = dt.strptime(end_date, "%d/%m/%Y")
# checks to see if dates are valid
if start_timestamp > end_timestamp or end_timestamp < start_timestamp:
errors.append('Please enter a valid date range')
else:
#checks to see if booking has already been taken
bookings = read_file('app/static/bookings.csv')
for i in bookings:
s_date = dt.strptime(i[0], "%d/%m/%Y")
e_date = dt.strptime(i[1], "%d/%m/%Y")
if s_date <= start_timestamp <= e_date:
errors.append('Booking has already been taken, please select another date')
break
# checks to see if email address is valid using regex
if not valid_email_address(email):
errors.append('Please enter a valid email address')
#if no errors have occured then write booking to file
if not errors:
new_booking = [start_date, end_date, name, email]
bookings.append(new_booking)
write_file(bookings, 'app/static/bookings.csv')
return render_template('booking.html')
return render_template('booking.html', errors=errors)
这是表单的模板：
<div id="main-wrapper">
<div id="main">
<div id="info">
{% if errors %}
{% for error in errors %}
<div><p>{{ error }}</p></div>
{% endfor %}
{% endif %}
<form action = "booking" method="post">
<input id="start_date" type="text" name="start_date">
<input id="end_date" type="text" name="end_date">
<input type="text" name="name" />
<input type="text" name="email" />
<input type="submit" value="Submit">
</div>
</div>
</div>
您最好使用表单库，例如WTForms http://wtforms.readthedocs.org/en/latest/（以及相关的扩展Flask-WTF https://flask-wtf.readthedocs.org/en/latest/）而不是手动完成这一切。
但如果您选择了这种方法，那么它就非常简单了。您需要将 request.form 中的值提供给 HTML 输入。
<input id="start_data" type="text" name="start_date" value="{{ request.form['start_date'] }}"/>
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