Don't insert spurious newlines in DummyTqdmFile.

Only call `tqdm.write` (which inserts a newline) if
`DummyTqdmFile.write` is itself called with a string containing a
newline; otherwise buffer the rest of the string.

See changes in test_tqdm.py for the patterns this allows.

tqdm/contrib/__init__.py

@@ -15,10 +15,18 @@
 
 class DummyTqdmFile(ObjectWrapper):
     """Dummy file-like that will write to tqdm"""
+    def __init__(self, wrapped):
+        super(DummyTqdmFile, self).__init__(wrapped)
+        self._buf = []
+
     def write(self, x, nolock=False):
-        # Avoid print() second call (useless \n)
-        if len(x.rstrip()) > 0:
-            tqdm.write(x, file=self._wrapped, nolock=nolock)
+        pre, sep, post = x.rpartition("\n")
+        if sep:
+            tqdm.write("".join(self._buf) + pre,
+                       file=self._wrapped, nolock=nolock)
+            self._buf = [post]
+        else:
+            self._buf.append(x)
 
 
 def tenumerate(iterable, start=0, total=None, tqdm_class=tqdm_auto,

tqdm/tests/tests_tqdm.py

@@ -2,6 +2,7 @@
 # Advice: use repr(our_file.read()) to print the full output of tqdm
 # (else '\r' will replace the previous lines and you'll see only the latest.
 
+from __future__ import print_function
 import sys
 import csv
 import re
@@ -1749,8 +1750,14 @@ def test_file_redirection():
     with closing(StringIO()) as our_file:
         # Redirect stdout to tqdm.write()
         with std_out_err_redirect_tqdm(tqdm_file=our_file):
-            for _ in trange(3):
+            with tqdm(total=3) as pbar:
                 print("Such fun")
+                pbar.update(1)
+                print("Such", "fun")
+                pbar.update(1)
+                print("Such ", end="")
+                print("fun")
+                pbar.update(1)
         res = our_file.getvalue()
         assert res.count("Such fun\n") == 3
         assert "0/3" in res