Select specific value for curl brace in f-string

January 31, 2022

I have the following f-string:

test = [51, 138]

for i in test:
    data = {
  'ajax': '{"tab_id":"t0","cur_page":1,"cur_trie":"distance","query":"","critere":{"id_marque":[f"{{str(i)}}"]},"sliders":{"prix":{"id":"#range_prix","face":"prix","max_counter":997748,"min":"1","max":"400000"},"km":{"id":"#range_km","face":"km","max_counter":1098088,"min":"1","max":"500000"},"millesime":{"id":"#range_millesime","face":"millesime","max_counter":1179169,"min":"1910","max":"2022"}},"req_num":2,"nb_results":"11964250","current_location_distance":-1,"logged_in":false}',
  'tabs': '["t0"]'
}

and I want to index the values as string from the list test in the list of values assigned to critere. However, I cannot properly index these values as the entire dictionary is a string, and there are multiple curly braces involved. How would I approach a situation like this?

The result I get it:

{'ajax': '{"tab_id":"t0","cur_page":1,"cur_trie":"distance","query":"","critere":{"id_marque":[f"{{str(i)}}"]},"sliders":{"prix":{"id":"#range_prix","face":"prix","max_counter":997748,"min":"1","max":"400000"},"km":{"id":"#range_km","face":"km","max_counter":1098088,"min":"1","max":"500000"},"millesime":{"id":"#range_millesime","face":"millesime","max_counter":1179169,"min":"1910","max":"2022"}},"req_num":2,"nb_results":"11964250","current_location_distance":-1,"logged_in":false}', 'tabs': '["t0"]'}
{'ajax': '{"tab_id":"t0","cur_page":1,"cur_trie":"distance","query":"","critere":{"id_marque":[f"{{str(i)}}"]},"sliders":{"prix":{"id":"#range_prix","face":"prix","max_counter":997748,"min":"1","max":"400000"},"km":{"id":"#range_km","face":"km","max_counter":1098088,"min":"1","max":"500000"},"millesime":{"id":"#range_millesime","face":"millesime","max_counter":1179169,"min":"1910","max":"2022"}},"req_num":2,"nb_results":"11964250","current_location_distance":-1,"logged_in":false}', 'tabs': '["t0"]'}

The expected output should be:

{'ajax': '{"tab_id":"t0","cur_page":1,"cur_trie":"distance","query":"","critere":{"id_marque":["51"]},"sliders":{"prix":{"id":"#range_prix","face":"prix","max_counter":997748,"min":"1","max":"400000"},"km":{"id":"#range_km","face":"km","max_counter":1098088,"min":"1","max":"500000"},"millesime":{"id":"#range_millesime","face":"millesime","max_counter":1179169,"min":"1910","max":"2022"}},"req_num":2,"nb_results":"11964250","current_location_distance":-1,"logged_in":false}', 'tabs': '["t0"]'}
{'ajax': '{"tab_id":"t0","cur_page":1,"cur_trie":"distance","query":"","critere":{"id_marque":["138"]},"sliders":{"prix":{"id":"#range_prix","face":"prix","max_counter":997748,"min":"1","max":"400000"},"km":{"id":"#range_km","face":"km","max_counter":1098088,"min":"1","max":"500000"},"millesime":{"id":"#range_millesime","face":"millesime","max_counter":1179169,"min":"1910","max":"2022"}},"req_num":2,"nb_results":"11964250","current_location_distance":-1,"logged_in":false}', 'tabs': '["t0"]'}

@Mozways answer is the solution I’m looking for; alternatively, here’s the example requested in the comment:

#following with your example
test = [51, 138]
another_test = [5, 10]

data = []
for i, j in zip(test, another_test):
    data.append({
  'ajax': '{"tab_id":...,"critere":{"id_marque":[%s], "id_color":[????]},"sliders":...}' % i, # how to implement j here also for id_color
  'tabs': '["t0"]'
})

>Solution :

If you really wanted to use a f-string, the whole string should be f'…'. Adding 'f"xxx"' in the middle of the string does not make it a f-string.

The issue here with f-strings is that it requires curly brackets, which would require you to heavily escape all the curly brackets of the JSON: something like f'{{"critere":{{"id_marque":[{i}]}}}}.

A simple way might be to use classical python string formatting: "abc%sefg" % "c".

Also, you need to use a list to store your dictionary or you will overwrite the dictionary again and again with the last loop element:

test = [51, 138]

data = []
for i in test:
    data.append({
  'ajax': '{"tab_id":...,"critere":{"id_marque":[%s]},"sliders":...}' % i,
  'tabs': '["t0"]'
})

output:

[{'ajax': '{"tab_id":...,"critere":{"id_marque":[51]},"sliders":...}',
  'tabs': '["t0"]'},
 {'ajax': '{"tab_id":...,"critere":{"id_marque":[138]},"sliders":...}',
  'tabs': '["t0"]'}]

several parameters:

test = [51, 138]
another_test = [5, 10]

data = []
for params in zip(test, another_test): # params should be in order
    data.append({
  'ajax': '{"tab_id":...,"critere":{"id_marque":[%s], "id_color":["%s"]},"sliders":...}' % params,
  'tabs': '["t0"]'
})

output:

[{'ajax': '{"tab_id":...,"critere":{"id_marque":[51], "id_color":["5"]},"sliders":...}',
  'tabs': '["t0"]'},
 {'ajax': '{"tab_id":...,"critere":{"id_marque":[138], "id_color":["10"]},"sliders":...}',
  'tabs': '["t0"]'}]

NB. if you need a more complex format, or variable order of the parameters, then a f-string with quoting is more appropriate