only get the default encoding one time

for the encode/decode functions, use a module-level cached value of the
default encoding given by encoding.getdefaultencoding(). This presumes
the value returned by getdefaultencoding isn't going to change over time.

IPython/utils/_process_win32.py

@@ -29,6 +29,7 b' from subprocess import STDOUT'
 from ._process_common import read_no_interrupt, process_handler, arg_split as py_arg_split
 from . import py3compat
 from . import text
+from .encoding import getdefaultencoding
 
 #-----------------------------------------------------------------------------
 # Function definitions
@@ -94,7 +95,7 b' def _find_cmd(cmd):'
 
 def _system_body(p):
     """Callback for _system."""
-    enc = py3compat.getdefaultencoding()
+    enc = getdefaultencoding()
     for line in read_no_interrupt(p.stdout).splitlines():
         line = line.decode(enc, 'replace')
         print(line, file=sys.stdout)

IPython/utils/py3compat.py

@@ -6,7 +6,9 b' import sys'
 import re
 import types
 
-from IPython.utils.encoding import getdefaultencoding
+from .encoding import getdefaultencoding
+
+default_encoding = getdefaultencoding()
 
 orig_open = open
 
@@ -14,11 +16,11 b' def no_code(x, encoding=None):'
     return x
 
 def decode(s, encoding=None):
-    encoding = encoding or getdefaultencoding()
+    encoding = encoding or default_encoding
     return s.decode(encoding, "replace")
 
 def encode(u, encoding=None):
-    encoding = encoding or getdefaultencoding()
+    encoding = encoding or default_encoding
     return u.encode(encoding, "replace")