I have an URL template of the form
https://farm{farm-id}.staticflickr.com/{server-id}/{photo-id}_{secret}.jpg
I have retrieved the following fields and there around 1000000 of these records. After retrieving the record below
farm-id: 1
server-id: 2
photo-id: 1418878
secret: 1e92283336
size: m
I need to construct this URL
https://farm1.staticflickr.com/2/1418878_1e92283336_m.jpg
I am thinking of some approaches, should I construct a dictionary for this one?
You can try using str.format(*args, **kwargs):
fmt = 'https://farm{farm-id}.staticflickr.com/{server-id}/{photo-id}_{secret}.jpg'
values = { 'farm-id': '1', 'server-id': 2, 'photo-id': '1418878', 'secret': '1e92283336', 'size': 'm' }
fmt.format(**values)
Everything surrounded with { and } in format string is called "replacement field". It ca be used with kwargs for such formatting. More info here.
A dictionary would probably be your best bet. As an alternative, check out named tuples.
Data = namedtuple('farm-id', 'server-id', 'photo-id', 'secret', 'size')
d = Data(1 ,2 ,1418878, 1e92283336, m)
I have managed to extract the data from the file and now I have two things, a fixed set of keys and a list of different values.
keys
['farm-id', 'server-id', 'photo-id', 'secret', 'originalformat', 'originalsecret']
values
['3', '2287', '2109698205', '20fbbcc947', 'jpg', '7a57411545']
['3', '2063', '2172469872', '8ddb85aedd', 'jpg', 'e12b952909']
['2', '1079', '830593398', '9ddca27ab0', 'jpg', 'bb91586e56']
['3', '2371', '2226919732', '248f23c5ff', 'jpg', '29f35fb0ca']
['2', '1014', '798067744', '4f043d2ea6', 'jpg', 'd739cc870b']
Is there a smarter way of merging these two lists into a dictionary after which I can use the formatting required to create the url
First of all, if your data is in the format you indicated you should make sure that numbers such as 1e92283336 can be interpreted are not interpreted in different way than you intended. For example with json
>>> json.loads('{"secret" : 1e92283336, "server_id" : 2, "farm_id": 1, "size" : "m"}')
{u'secret': inf, u'farm_id': 1, u'server_id': 2, u'size': u'm'}
After you successfully imported the fields to a dictionary there are multiple ways you can use string interpolation and formatting. Apart from the str.format specifier mentioned in previous answer you can use the traditional % style formatting as below (note the format specifier s after the closing parentheses)
>>> url = "https://farm%(farm-id)s.staticflickr.com/%(server-id)s/%(photo-id)s_%(secret)s.jpg"
>>> print url % {'secret': '1e92283336', 'server-id': '2', 'farm-id': '1', 'size': 'm', 'photo-id' : '1418878'}
https://farm1.staticflickr.com/2/1418878_1e92283336.jpg
You can also use Template Strings which uses the Template class from the string module. This would be more familiar to bash/perl programmers. The template string is of the form below. The placeholders (within optional braces) must be valid python identifiers so it cannot contain characters such as -. The first non-identifier character terminates the placeholder. With safe_substitute method if any placeholder value is missing it will put the original placeholder instead of raising a key error.
>>> from string import Template
>>> s = Template("https://farm${farm_id}.staticflickr.com/${server_id}/${photo_id}_${secret}.jpg")
>>> s.substitute({'secret': '1e92283336', 'server_id': '2', 'farm_id': '1', 'size': 'm', 'photo_id' : '1418878'})
'https://farm1.staticflickr.com/2/1418878_1e92283336.jpg'
>>> s.safe_substitute({'server_id': '2', 'farm_id': '1', 'size': 'm', 'photo_id' : '1418878'})
'https://farm1.staticflickr.com/2/1418878_${secret}.jpg'
