Automatic numbering increases costs
bad
print “{} is {}”.format(“life”,”hard”)
good
print “{0} is {1}”.format(“life”,”hard”)
Why you should care
If you are not numbering your replacement fields {} in your format string, Python auto-numbers them. For example, using “{} {}” is interpreted as {0} {1}. This is correct code, but is hard to read if you use a large number of parameters. If a format string is particularly long, it is difficult to tell which replacement fields relate to which argument of your format string. Especially if code is refactored, unnumbered replacement fields are often not in sync with the arguments of the format string.
Business Impacts
It is recommended to avoid these in order to ensure the code is more readable and cost effective.
CAST recommendations
References
https://www.quantifiedcode.com/knowledge-base/maintainability/Explicitly%20number%20replacement%20fields%20in%20a%20format%20string/3aSZNLMu
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