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pythonrpython-3.xstringrpy2

Strange behaviour with string passing to rpy2 - deleting leading zeros from string

I am trying to call a python string variable within a rpy2 script. The variable is supposed to have the shape "01".

I encountered the following behaviour:

import rpy2.robjects as robjects
string_to_pass = "01"
robjects.r('''print(paste("Output from R with format and paste:",{}))'''.format(string_to_pass))

will give the following output:

[1] "Output from R with format and paste: 1"

Note, that the leading zero of the string was cut off.

On the other side, these lines will work as expected:

print("Output from python with format: {}".format(string_to_pass))
robjects.r('''print("Output from R with format: {}")'''.format(string_to_pass))
robjects.r('''print(paste("Output from R with pasting a string:", "01"))''')

with the output:

Output from python with format: 01
[1] "Output from R with format: 01"
[1] "Output from R with pasting a string: 01"

Can sombody please explain what is happening here, only when combining python .format() and r paste(), and how to avoid it?

Solution

  • I have solved the problem by saying

    string_to_pass = "'01'"
robjects.r('''print(paste("Output from R with format and paste:",{}))'''.format(string_to_pass))

    Note the additional inner quotation marks which seem to be important for R to recognize it as a string aswell.