msp() and mp() got the columns wrong in header (#50)

Author: endrebak

CHANGELOG.txt

@@ -1,4 +1,5 @@
-# 0.0.58 (24.10.19)
+# 0.0.58 (25.10.19)
+- fix merge print functions
 - make pickleable
 - add iter as alias for itergrs in pr. namespace
 - gr.length() shows nucleotide length (sum of all interval lengths)

pyranges/tostring2.py

@@ -302,11 +302,16 @@ def tostring(self, n=8, merge_position=False, formatting=None, sort=False):
 
     if merge_position:
         df = show_pos_merge_position(df)
-        columns_dtypes["- Position -"] = "Multiple types"
         for k in "Chromosome Start End Strand".split():
             if k in columns_dtypes:
                 del columns_dtypes[k]
 
+        _columns_dtypes = {}
+        _columns_dtypes["- Position -"] = "Multiple types"
+        for k, v in columns_dtypes.items():
+            _columns_dtypes[k] = v
+        columns_dtypes = _columns_dtypes
+
     df = df.astype(object).reset_index(drop=True)
     if len(self) > n:
         middle = int(n / 2)