findpython is an R package that finds acceptable Python
binaries for your program. Since there are often multiple python
binaries installed on any given system and they aren't always added to
the path this can be a non-trivial task.
To install the latest version released to CRAN use:
install.packages("findpython")To install the development version use:
remotes::install_github("trevorld/findpython")It has no dependencies (other than R) but if you have the suggested
reticulate package installed it will also use it to try to
find an acceptable python binary. You'll also need the suggested
testthat package to run the unit tests.
find_python_cmd is the main function. It returns the
path to a python binary that meets certain requirements you specify.
Below are some examples.
If you need to find a Python 2 binary which is at least Python 2.4:
> library("findpython")
> find_python_cmd(minimum_version = '2.4', maximum_version = '2.7')
[1] "/usr/bin/python"If you need to find a version of Python at least Python 2.5 (but don't care if it is a Python 3 binary):
> find_python_cmd(minimum_version = '2.5')
[1] "/usr/bin/python"If you don't care what version of Python you use but it needs to have
access to an argparse module as well as either the
json OR simplejson module:
> find_python_cmd(required_modules = c('argparse', 'json | simplejson'))
[1] "/usr/bin/python"Although find_python_cmd will create a basic default
message if left unspecified you can use the error_message
argument to specify what error message your program will output if it is
unable to find an acceptable binary:
> error_message <- paste('Was unable to find the Python 4 binary dependency.',
+ 'See file INSTALL for more information.')
> find_python_cmd(minimum_version = '4.0', error_message = error_message)
Error in find_python_cmd(minimum_version = "4.0", error_message = error_message) :
Was unable to find the Python 4 binary dependency. See file INSTALL for more information.There is also a wrapper for find_python_cmd that instead
of throwing an error upon failing to find an appropriate Python command
will return FALSE and if it finds an appropriate command
will return TRUE. If successful it attaches the appropriate
binary path as an attribute python_cmd:
> did_find_python <- can_find_python_cmd()
> python_cmd <- attr(did_find_python, "python_cmd")
> cat(did_find_python, python_cmd, "\n")
TRUE /usr/bin/pythonThe default error message will be something like:
> find_python_cmd(min='4.0')
Error in find_python_cmd(min = "4.0") :
Couldn't find a sufficient Python binary. If you haven't installed the Python dependency yet please do so. If you have but it isn't on the system path (as is default on Windows) please add it to path or set options('python_cmd'='/path/to/binary') or set the PYTHON, PYTHON2, or PYTHON3 environmental variables. Python must be at least version 4.0 If you already have a python binary you want to check you can use
is_python_sufficient to test whether it has sufficient
features. It has the same arguments minimum_version,
maximum_version, and required_modules as
find_python_cmd:
> is_python_sufficient(path_to_binary, minimum_version = '2.6', required_modules = 'scipy')
[1] FALSEThis package is available under the MIT license.