Avoid loading libpython.so if Python symbols are already loaded globally

src/PyCall.jl

@@ -36,14 +36,55 @@ const depfile = joinpath(dirname(@__FILE__), "..", "deps", "deps.jl")
 isfile(depfile) || error("PyCall not properly installed. Please run Pkg.build(\"PyCall\")")
 include(depfile) # generated by Pkg.build("PyCall")
 
+hassym(lib, sym) = Libdl.dlsym_e(lib, sym) != C_NULL
+
+function get_globaldl()
+    if !isdefined(:globaldl)
+        global const globaldl = unsafe_load(cglobal((@windows ? :jl_exe_handle : :jl_dl_handle), Ptr{Void}))
+    end
+    return globaldl
+end
+
+
+function get_libpythondl()
+    if !isdefined(:libpythondl)
+        global const libpythondl = Libdl.dlopen(libpython, Libdl.RTLD_GLOBAL)
+    end
+    return libpythondl
+end
+
+
 macro pysym(func)
-    :(($func, libpython))
+    z, zlocal = gensym(string(func)), gensym()
+    eval(current_module(),:(global $z = C_NULL))
+    z = esc(z)
+
+    quote
+        let $zlocal::Ptr{Void} = $z::Ptr{Void}
+            if $zlocal == C_NULL
+               if hassym(get_globaldl(), $(esc(func)))
+                   $zlocal = Libdl.dlsym(globaldl::Ptr{Void}, $(esc(func)))
+               else
+                   $zlocal = Libdl.dlsym(get_libpythondl()::Ptr{Void}, $(esc(func)))
+               end
+               global $z = $zlocal
+            end
+            $zlocal
+        end
+    end
 end
+
 macro pyglobal(name)
-    :(cglobal(($name, libpython)))
+    quote
+        if hassym(get_globaldl(), $(esc(name)))
+            Libdl.dlsym(globaldl::Ptr{Void}, $(esc(name)))
+        else
+            Libdl.dlsym(get_libpythondl()::Ptr{Void}, $(esc(name)))
+        end
+    end
 end
 macro pyglobalobj(name)
-    :(cglobal(($name, libpython), PyObject_struct))
+    :(convert(PyPtr, @pyglobal $(esc(name))))
 end
 
 #########################################################################

src/exception.jl

@@ -98,7 +98,11 @@ const pyexc = Dict{DataType, PyPtr}()
 type PyIOError <: Exception end
 
 macro pyglobalobjptr(name)
-    :(unsafe_load(cglobal(($name, libpython), Ptr{PyObject_struct})))
+    quote
+        sym = @pyglobal $name
+        ptr = convert(Ptr{PyPtr}, sym)
+        unsafe_load( ptr )
+    end
 end
 
 function pyexc_initialize()

src/pyinit.jl

@@ -23,12 +23,15 @@ const MethodWrapperType = PyNULL()
 const ufuncType = PyNULL()
 const format_traceback = PyNULL()
 
+
 #########################################################################
 
 function __init__()
-    # issue #189
-    Libdl.dlopen(libpython, Libdl.RTLD_LAZY|Libdl.RTLD_DEEPBIND|Libdl.RTLD_GLOBAL)
-
+    # Check to see if the Python symbols are already defined in the global namespace of the current
+    # process before we try to load them from a dynamic library.
+    if !hassym(get_globaldl(), :Py_GetVersion)
+        Libdl.dlopen(libpython, Libdl.RTLD_LAZY|Libdl.RTLD_DEEPBIND|Libdl.RTLD_GLOBAL)
+    end
     already_inited = 0 != ccall((@pysym :Py_IsInitialized), Cint, ())
 
     if !already_inited