Question

I have two methods that I’m using as custom tags in a template engine:

# Renders a <select> form field def select_field(options, selected_item, field_name):     options = [(str(v),str(v)) for v in options]     html = ['<select name='%s'>' % field_name]     for k,v in options:         tmp = '<option '         if k == selected_item:             tmp += 'selected '         tmp += 'value='%s'>%s</option>' % (k,v)         html.append(tmp)     html.append('</select>')     return '\n'.join(html)  # Renders a collection of <select> fields for datetime values def datetime_field(current_dt, field_name):     if current_dt == None:         current_dt = datetime.datetime.now()     day = select_field(range(1, 32), current_dt.day, field_name + '_day')     month = select_field(range(1, 13), current_dt.month, field_name + '_month')     year = select_field(range(datetime.datetime.now().year, datetime.datetime.now().year + 10), current_dt.year, field_name + '_year')     hour = select_field(range(1, 13), current_dt.hour, field_name + '_hour')     minute = select_field(range(1, 60), current_dt.minute, field_name + '_minute')     period = select_field(['AM', 'PM'], 'AM', field_name + '_period')     return '\n'.join([day, '/', month, '/', year, ' at ', hour, ':', minute, period]) 

As you can see in the comments, I’m attempting to generate select fields for building a date and time value.

My first question is, how do I make the day, month, hour, and minute ranges use two digits? For example, the code generates ‘1, 2, 3…’ while I would like ’01, 02, 03′.

Next, when the fields get generated, the values of the supplied datetime are not selected automatically, even though I’m telling the select_field method to add a ‘selected’ attribute when the value is equal to the supplied datetime’s value.

Finally, how do I get the 12-hour period identifier (AM/PM) for the supplied datetime? For the moment, I’m simply selecting ‘AM’ by default, but I would like to supply this value from the datetime itself.

Answer 1

To turn an integer range into two digit strings:

>>> range(13) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12] >>> [ '%02d' % i for i in range(13) ] ['00', '01', '02', '03', '04', '05', '06', '07', '08', '09', '10', '11', '12'] 

Then to get the AM/PM indicator:

>>> import datetime >>> current_dt = datetime.datetime.now() >>> current_dt datetime.datetime(2009, 2, 4, 22, 2, 14, 390000) >>> ['AM','PM'][current_dt.hour>=12] 'PM' 

Voila!