Avoid duplicating arguments to str.format?

Question

I'm currently using string formatting in my code however I find that I'm hard coding to display repeated variables. Is there a more efficient way to do this

print("Hello this is {} and {} and {} - Hello this is {} and {} and {} ".format(versionP, versionS, versionT, versionP, versionS, versionT))

The outcome is the one I want but I need to repeat this in several instances and can become tedious. Is there a way to only write the variable once?

This depends on your Python version. F-strings, as proposed by Aaron_ab, are available from 3.6 onward. — Bram Vanroy
– Bram Vanroy, Commented Jan 8, 2019 at 15:56

cs95 · Accepted Answer · 2019-01-08 16:01:28Z

8

You can specify positions, and str.format will know which arguments to use:

a, b, c = 1, 2, 3
string = "This is {0}, {1}, and {2}. Or, in reverse: {2}, {1}, {0}"
string.format(a, b, c)
# 'This is 1, 2, and 3. Or, in reverse: 3, 2, 1'

You may also pass keyword arguments, or unpack a dictionary:

a, b, c = 1, 2, 3
string = """This is {versionP}, {versionS}, and {versionT}. 
            Or, in reverse: {versionT}, {versionS}, {versionP}"""
# string.format(versionP=a, versionS=b, versionT=c)
string.format(**{'versionP': a, 'versionS': b, 'versionT': c})
# This is 1, 2, and 3. 
#       Or, in reverse: 3, 2, 1

edited Jan 8, 2019 at 16:01

answered Jan 8, 2019 at 15:53

cs95

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2 Comments

Aaron_ab Over a year ago

Notice the tecenique with the dictionary can raise exception when have no relevant keys in the dict to place..

cs95 Over a year ago

Note to OP: I have converted my answer into runnable examples so you can see for yourself how this works. The process is identical for your use case.

cs95 · Accepted Answer · 2019-01-12 22:57:20Z

6

Python 3.6

I find it clean and simple:

print(f"Hello this is {versionP} and {versionS} and {versionT} - 
        Hello this is {versionP} and {versionS} and {versionT}")

You can even evaluate methods inside f-formatting or nested f-strings

edited Jan 12, 2019 at 22:57

cs95

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answered Jan 8, 2019 at 15:55

Aaron_ab

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2 Comments

cs95 Over a year ago

Good answer, but this assumes OP has python3.6

Aaron_ab Over a year ago

Good point. This will work only in 3.6 and above.. I like your answer as well with the dictionary

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