(self, envstr)
return self
Add string with key=val to Uenv if key non-existent
Add string with key=val to Uenv if key non-existent
Add string with key = val to Uenv if key non - existent
def appendif(self, envstr):
        """Add string with key=val to Uenv if key non-existent"""
        (key, val) = get_pair(envstr)
        if key and key not in self.env:
            self.env[key] = val
        return self
def appendif ( self , envstr ) : ( key , val ) = get_pair ( envstr ) if key and key not in self . env : self . env [ key ] = val return self