Truncate long variables in the middle

pysnooper/utils.py

@@ -54,11 +54,17 @@ def get_shortish_repr(item):
     except Exception:
         r = 'REPR FAILED'
     r = r.replace('\r', '').replace('\n', '')
-    if len(r) > MAX_VARIABLE_LENGTH:
-        r = '{truncated_r}...'.format(truncated_r=r[:MAX_VARIABLE_LENGTH])
+    r = truncate(r, MAX_VARIABLE_LENGTH)
     return r
 
 
+def truncate(string, max_length):
+    if len(string) > max_length:
+        left = (max_length - 3) // 2
+        right = max_length - 3 - left
+        string = u'{}...{}'.format(string[:left], string[-right:])
+    return string
+
 
 def ensure_tuple(x):
     if isinstance(x, six.string_types):

tests/test_pysnooper.py

@@ -6,6 +6,7 @@ import textwrap
 import threading
 import types
 
+from pysnooper.utils import truncate
 from python_toolbox import sys_tools, temp_file_tools
 import pytest
 
@@ -384,15 +385,16 @@ def test_long_variable():
         result = my_function()
     assert result == list(range(1000))
     output = output_capturer.string_io.getvalue()
+    regex = r'^\[0, 1, 2, .*\.\.\..*, 997, 998, 999\]$'
     assert_output(
         output,
         (
             CallEntry('def my_function():'),
             LineEntry('foo = list(range(1000))'),
-            VariableEntry('foo', value_regex=r'''^\[0, 1, 2, .*\.\.\.$'''),
+            VariableEntry('foo', value_regex=regex),
             LineEntry(),
             ReturnEntry(),
-            ReturnValueEntry(value_regex=r'''^\[0, 1, 2, .*\.\.\.$''')
+            ReturnValueEntry(value_regex=regex)
         )
     )
 
@@ -918,3 +920,15 @@ def test_with_block_depth():
             ReturnValueEntry('20'),
         )
     )
+
+
+def test_truncate():
+    max_length = 20
+    for i in range(max_length * 2):
+        string = i * 'a'
+        truncated = truncate(string, max_length)
+        if len(string) <= max_length:
+            assert string == truncated
+        else:
+            assert truncated == 'aaaaaaaa...aaaaaaaaa'
+            assert len(truncated) == max_length