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

Answer 1

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.