Python multiline string format

Question

I'm trying to have a script to generate some makefiles for me. I want to format this multiline string, but I'm getting a strange error.

Code:

make_content = """ PCC = pgcc 
%(bench)_serial: src/main.c src/%(bench)_serial.c ../common/util.c
\t$(PCC) $(ACCFLAGS) -o bin/%(bench)_serial src/main.c src/%(bench)_serial.c

clean:
\trm -rf *.o *.oo bin/*""" % {'bench':'umpalumpa'}

Error:

Traceback (most recent call last):
  File "./new_bench.py", line 27, in <module>
    \trm -rf *.o *.oo bin/*""" % {'bench':'umpalumpa'}
ValueError: unsupported format character '_' (0x5f) at index 21

Any ideas?

Notes: this is a truncated version of the makefile, no comments on that. Notes[2]: 'umpalumpa' is a placeholder to make sure it's a string. It'll be something real one day.

Edit: I'm using python 2.7

Rohit Jain · Accepted Answer · 2012-10-23 05:25:55Z

6

As you have already got the answer as to why that didn't work, a better way and also recommended to use if format function (If you are using `Python 2.6+): -

"src/{bench}_serial.c".format(bench='umpalumpa')

So, for your string, it becomes: -

ake_content = """ PCC = pgcc 
{bench}_serial: src/main.c src/{bench}_serial.c ../common/util.c
\t$(PCC) $(ACCFLAGS) -o bin/{bench}_serial src/main.c src/{bench}_serial.c

clean:
\trm -rf *.o *.oo bin/*""".format(bench='umpalumpa')

answered Oct 23, 2012 at 5:25

Rohit Jain

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3 Comments

agf Over a year ago

This doesn't really answer his question of why he's getting that error. It also only works in Python 2.6+, so while usually fine, it can cause compatibility problems if older versions of Python need to be supported.

Rohit Jain Over a year ago

@agf. I just posted it, because his problem was already solved by prevoius answer. and there is no point in duplicating the answer. right?

Rohit Jain Over a year ago

@agf. I think this answer is far eligible to stand as answer, rather than a comment.

agf · Accepted Answer · 2012-10-23 05:22:07Z

5

You need to specify a conversion type after the mapping key:

"%(bench)s_serial" % {'bench':'umpalumpa'}

Note the s before the underscore. The output here would still be "umpalumpa_serial".

The conversion type is always required and always last, after the % and any optional components.

There is no difference between formatting a triple-quoted string literal and a single quoted string literal.

answered Oct 23, 2012 at 5:22

agf

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