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 setPPSS(self, p1, p3, lenp1, lenp3):
        temp = []
        self.p1 = p1
        self.p3 = p3
        self.lenp1 = lenp1
        self.lenp3 = lenp3

        #bp3 is the angle beside p3 point, cp3 is the angle for line23, p2 is the output
        line31 = Line(p3, p1)
        self.lenp2 = line31.getR()
        #self.lenp2 = self.p3.distance(self.p1)
        #這裡是求角3
        ap3 = math.acos(((self.lenp1 * self.lenp1 + self.lenp2 * self.lenp2) - self.lenp3 * self.lenp3) / (2 * self.lenp1 * self.lenp2))
        #ap3 = math.acos(((self.lenp1 * self.lenp1 + self.lenp3 * self.lenp3) - self.lenp2 * self.lenp2) / (2 * self.lenp1 * self.lenp3))
        bp3 = line31.getT()
        cp3 = bp3 - ap3
        temp.append(p3.x + self.lenp1*math.cos(cp3))#p2.x
        temp.append(p3.y + self.lenp1*math.sin(cp3))#p2.y
        return temp