def install_pip(self, package, save=True, save_dev=False):
        """Installs a pip package.

        :param save: if `True`, pins the package to the Hydrogen requirements
            YAML file.
        :param save_dev: if `True`, pins the package as a development
            dependency to the Hydrogen requirements YAML file.
        :param return: a **single** :class:`Requirement` object, representing
            the installed version of the given package.
        """
        requirement = Requirement.coerce(package)
        click.echo("pip install " + requirement.package)
        cmd = envoy.run("pip install {}".format(str(requirement)))
        if cmd.status_code == 0:
            installed_packages = get_installed_pypackages()
            package = installed_packages[requirement.package]
            requirement.version = "=={}".format(package.version)
            if save:
                self.requirements["all"].add(requirement)
            if save_dev:
                self.requirements["dev"].add(requirement)
            if save or save_dev:
                self.requirements.save()
            return requirement
        else:
            fatal(cmd.std_err)
def test_ccode_Pow():
    assert ccode(x**3) == "pow(x, 3)"
    assert ccode(x**(y**3)) == "pow(x, pow(y, 3))"
    assert ccode(1/(g(x)*3.5)**(x - y**x)/(x**2 + y)) == \
        "pow(3.5*g(x), -x + pow(y, x))/(pow(x, 2) + y)"
    assert ccode(x**-1.0) == '1.0/x'
    assert ccode(x**Rational(2, 3)) == 'pow(x, 2.0L/3.0L)'
    _cond_cfunc = [(lambda base, exp: exp.is_integer, "dpowi"),
                   (lambda base, exp: not exp.is_integer, "pow")]
    assert ccode(x**3, user_functions={'Pow': _cond_cfunc}) == 'dpowi(x, 3)'
    assert ccode(x**3.2, user_functions={'Pow': _cond_cfunc}) == 'pow(x, 3.2)'