Use global session

pygmt/__init__.py

@@ -26,7 +26,6 @@
 from pygmt.accessors import GMTDataArrayAccessor
 from pygmt.figure import Figure, set_display
 from pygmt.io import load_dataarray
-from pygmt.session_management import begin as _begin
 from pygmt.session_management import end as _end
 from pygmt.src import (
     binstats,
@@ -66,7 +65,5 @@
     xyz2grd,
 )
 
-# Start our global modern mode session
-_begin()
 # Tell Python to run _end when shutting down
 _atexit.register(_end)

pygmt/_state.py

@@ -0,0 +1,10 @@
+"""
+Private dictionary to keep tracking of current PyGMT state.
+
+The feature is only meant for internal use by PyGMT and is experimental!
+"""
+
+_STATE = {
+    "session_name": None,
+    "module_calls": None,
+}

pygmt/clib/session.py

@@ -7,6 +7,7 @@
 
 import contextlib
 import ctypes as ctp
+import os
 import pathlib
 import sys
 import warnings
@@ -17,6 +18,7 @@
 import pandas as pd
 import xarray as xr
 from packaging.version import Version
+from pygmt._state import _STATE
 from pygmt.clib.conversion import (
     array_to_datetime,
     as_c_contiguous,
@@ -33,6 +35,7 @@
     data_kind,
     tempfile_from_geojson,
     tempfile_from_image,
+    unique_name,
 )
 
 FAMILIES = [
@@ -209,6 +212,10 @@ def __enter__(self):
 
         Calls :meth:`pygmt.clib.Session.create`.
         """
+        # This is the first time a Session object is created.
+        if _STATE["session_name"] is None:
+            # Set GMT_SESSION_NAME to a customized, unique value.
+            _STATE["session_name"] = os.environ["GMT_SESSION_NAME"] = unique_name()
         self.create("pygmt-session")
         return self
 
@@ -623,6 +630,12 @@ def call_module(self, module: str, args: str | list[str]):
         GMTCLibError
             If the returned status code of the function is non-zero.
         """
+        if _STATE["module_calls"] is None:
+            from pygmt.session_management import begin
+
+            _STATE["module_calls"] = []
+            begin()
+
         c_call_module = self.get_libgmt_func(
             "GMT_Call_Module",
             argtypes=[ctp.c_void_p, ctp.c_char_p, ctp.c_int, ctp.c_void_p],
@@ -651,6 +664,7 @@ def call_module(self, module: str, args: str | list[str]):
                 "'args' must be either a string or a list of strings."
             )
 
+        _STATE["module_calls"].append(module)
         status = c_call_module(self.session_pointer, module.encode(), mode, argv)
         if status != 0:
             raise GMTCLibError(

pygmt/session_management.py

@@ -2,11 +2,8 @@
 Modern mode session management modules.
 """
 
-import os
-import sys
-
+from pygmt._state import _STATE
 from pygmt.clib import Session
-from pygmt.helpers import unique_name
 
 
 def begin():
@@ -17,10 +14,6 @@ def begin():
 
     Only meant to be used once for creating the global session.
     """
-    # On Windows, need to set GMT_SESSION_NAME to a unique value
-    if sys.platform == "win32":
-        os.environ["GMT_SESSION_NAME"] = unique_name()
-
     prefix = "pygmt-session"
     with Session() as lib:
         lib.call_module(module="begin", args=[prefix])
@@ -37,5 +30,11 @@ def end():
     background, convert them to the desired format (specified in
     ``pygmt.begin``), and bring the figures to the working directory.
     """
+    if _STATE["session_name"] is not None:
+        return
+
     with Session() as lib:
         lib.call_module(module="end", args=[])
+
+    # Reset the sesion name to None
+    _STATE["session_name"] = None