Django, return a value to the HTML file from a view when using a form

Question

My index.html file contains three forms, each connect to my views.py file and perform some function, everything is working fine but I am not understanding how to get a returned value back to my html page to display it.

index.html:

<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Index</title>
</head>
<body>
    
    <form action="{% url 'start_or_end_fast' %}" method="POST">
        {% csrf_token %} 
        <button type="submit" name='start_fast' value='start_fast'>Add Fast</button>
    </form>

    <form action="{% url 'start_or_end_fast' %}" method="POST">
        {% csrf_token %} 
        <button type="submit" name='end_fast' value='end_fast'>End Fast</button>
    </form>

    <form action="{% url 'start_or_end_fast' %}" method="POST">
        {% csrf_token %} 
        <button type="submit" name='duration' value='duration'>Fast Duration</button>
    </form>

<!-- DISPLAY FAST DURATION ON THE PAGE -->
{% if duration %}
      <p>Fasting for {{duration}} </p>
{% endif %}
    
</body>
</html>

The third form is a button, when I press it the duration prints in the terminal. views.py code to do that:

#If pressing Fast Duration button, show the duration difference between the current fast start_date_time and the current time 
  elif request.method == 'POST' and 'duration' in request.POST:

   time_difference()
   return render(request,'startandstoptimes/index.html')

  else:
   return render(request,'startandstoptimes/index.html')


def time_difference():

   #Get the current date and time 
   current_time = datetime.now().strftime(("%Y-%m-%d %H:%M:%S"))
   time_now = datetime.strptime(current_time, "%Y-%m-%d %H:%M:%S")

   #find the current fast that has not finished yet 
   #Get the date and time of that fast
   get_start_date_time = logTimes.objects.get(fast_finished = False)
   fast_started = get_start_date_time.start_date_time
   
   #caluclate the difference between the start of the fast and the time right now
   difference = time_now - fast_started
   duration = difference.total_seconds() 
   days    = divmod(duration, 86400)      # Get days (without [0]!)
   hours   = divmod(days[1], 3600)        # Use remainder of days to calc hours
   minutes = divmod(hours[1], 60)         # Use remainder of hours to calc minutes
   seconds = divmod(minutes[1], 1)
   
   difference_less_microseconds = str(difference).split(".")[0]
   print(difference_less_microseconds)

Output in the terminal:

1:15:20
[12/Jul/2022 23:14:48] "POST /startandstoptimes/ HTTP/1.1" 200 1139

I am wondering if I need to use HttpResponse instead of request?

I have been researching and experimenting but the examples I find are a bit more complicated than what I am trying to achieve.

JanMalte · Accepted Answer · 2022-07-12 21:26:28Z

1

You have to use the context for the template rendering to pass variables to the template.

views.py

  # ... your code
  elif request.method == 'POST' and 'duration' in request.POST:
    duration = time_difference()
    return render(request,'startandstoptimes/index.html', {'duration': duration})

Your time_difference() function has to return the value you like to diplay in the template

def time_difference():
   # ... your code
   difference_less_microseconds = str(difference).split(".")[0]
   return difference_less_microseconds

answered Jul 12, 2022 at 21:26

JanMalte

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1 Comment

deucalion0 Over a year ago

I tried this but was missing passing back the value from my function to use in the context, now it works and it makes perfect sense!!! Many thanks for your help with this, I was close but not quite there :)

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