CODEWITHSUNDEEP
pythonpython-3.xstring
Shan-Desai
Shan-Desai

Reputation: 3349

Trouble using tuple along with other strings when passing them to .format in Python within a string

I have the following TOML:

[gps]
measurement = "gps"
tags = ["lat", "lon", "alt"]
limit = 10

which translates to the following dictionary in Python:

{
  "gps": {
       "measurement": "gps",
       "tags": [ "lat", "lon", "alt"],
       "limit": 10
}

I have a class where I wish to create a member function read_gps as follows:

  1. get the **kwargs from above dict
  2. currently, just print the following string: select "lat", "lon", "alt", from "gps" limit 10

code

class dbClass:
    def __init__(self, db=None, **kwargs):
        self.kwargs = kwargs # this kwargs is different from the above kwargs
        # do some initialization stuff here

     def read_gps(self, **kwargs):
        # pass the above mentioned dict here
        # instance_dbClass.read_gps(gps_dict)

        _data = kwargs
        _tags = kwargs.get('tags')

        print('select "{}","{}","{}" from "{}" limit {}'.format(*_tags,
                          _data.get('measurement'), 
                          _data.get('limit'))
        )

But I get the following error:

SyntaxError: only named arguments may follow *expression

On the contrary, if i remove the measurement and limit it would work fine.

What is a pythonic way to achieve this? should i create two different strings and then in the end concatenate them?

Trial

query = """
        select "{}", "{}", "{}" from "{}" limit {}
        """.format(_tags[0], _tags[1], _tags[2], _data.get('measurement'),
                   _data.get('limit'))
print(query)

works however it there a way to use the * unpacking for tuple within the .format() along with the other values

Upvotes: 0

Views: 559

Answers (1)

jfhr
jfhr

Reputation: 1133

Your code will work in Python version 3.5+, following Pep 448. If you have to use a version lower than 3.5, you can use named parameters:

print(select "{}","{}","{}" from "{measurement}" limit {limit}'.format(*_tags, measurement=measurement, limit=limit))

Alternatively, join the _tags into a single string first:

print('select "{}" from "{}" limit {}'.format('","'.join(_tags), measurement, limit))

The second option will work even if the length of _tags changes.

Upvotes: 3

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