How to avoid 'f-string: expressions nested too deep' error when using f-string in Python?

In Python programming, f-string string formatting is powerful and convenient, but sometimes you will encounter the "f-string: expressions nested too deep" error. This error usually results from the nested curly braces {} in f-string that cause parsing conflicts, especially when dealing with strings of JSON structures.

For example, the following code snippet might throw this error:

 tmp = "Downhill"
s1 = f'{"music.search.searchcgiservice": {"method": "dosearchforqqmusicdesktop","module": "music.search.searchcgiservice","param": {"num_per_page": 40,"page_num": 1,"query": {tmp},"search_type": 0}}}'

This is because f-string interprets {} as an expression, and the JSON structure itself also uses {} , causing parsing ambiguity.

The solution is to avoid directly embedding complex JSON structures in f-string. It is recommended to use the json.dumps() function to convert the dictionary to a JSON string and insert it into a f-string:

 import json

tmp = "Downhill"
data = {
    "music.search.searchcgiservice": {
        "method": "dosearchforqqmusicdesktop",
        "module": "music.search.searchcgiservice",
        "param": {
            "num_per_page": 40,
            "page_num": 1,
            "query": tmp,
            "search_type": 0
        }
    }
}
s1 = f"{json.dumps(data)}"

This method clearly separates the data and string formatting, avoids the parsing problems caused by nested curly braces, while maintaining the readability and maintainability of the code. json.dumps() ensures that the JSON structure is correctly formatted, avoiding possible errors that may occur when manually splicing strings.

Another approach is to use traditional string formatting methods such as % operator or str.format() method, but json.dumps() method is more recommended because it is clearer, less error-prone, and is more suitable for handling JSON data.

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