Use uuid.uuid4 to generate unique names (#274)

Use `uuid.uuid4().hex` to generate unique names.

Fixes #273

Author: seisman

pygmt/helpers/tempfile.py

@@ -2,27 +2,26 @@
 Utilities for dealing with temporary file management.
 """
 import os
+import uuid
 from tempfile import NamedTemporaryFile
 
 import numpy as np
 
 
 def unique_name():
     """
-    Generate a unique name with the prefix 'gmt-python-'.
+    Generate a unique name.
 
     Useful for generating unique names for figures (otherwise GMT will plot
     everything on the same figure instead of creating a new one).
 
     Returns
     -------
     name : str
-        A unique name generated by ``tempfile.NamedTemporaryFile``
+        A unique name generated by :func:`uuid.uuid4`
 
     """
-    # Use the tempfile module to generate a unique name.
-    with NamedTemporaryFile(prefix="gmt-python-") as tmpfile:
-        return os.path.split(tmpfile.name)[-1]
+    return uuid.uuid4().hex
 
 
 class GMTTempFile:

pygmt/tests/test_helpers.py

@@ -10,9 +10,8 @@
 
 
 def test_unique_name():
-    "Make sure the names start with gmt-python- and are really unique"
+    "Make sure the names are really unique"
     names = [unique_name() for i in range(100)]
-    assert all([name.startswith("gmt-python-") for name in names])
     assert len(names) == len(set(names))