diff --git a/hgext/convert/p4.py b/hgext/convert/p4.py
--- a/hgext/convert/p4.py
+++ b/hgext/convert/p4.py
@@ -177,7 +177,7 @@ class p4_source(converter_source):
                     elif "k" in flags:
                         keywords = self.re_keywords
 
-            elif code == "text" or code == "binary":
+            elif code in ("text", "binary"):
                 contents += data
 
         if mode is None:
diff --git a/mercurial/ancestor.py b/mercurial/ancestor.py
--- a/mercurial/ancestor.py
+++ b/mercurial/ancestor.py
@@ -34,7 +34,7 @@ def ancestor(a, b, pfunc):
             visit.pop()
         else:
             for p in pl:
-                if p == a or p == b: # did we find a or b as a parent?
+                if p in (a, b): # did we find a or b as a parent?
                     return p # we're done
                 if p not in depth:
                     visit.append(p)
diff --git a/mercurial/dagparser.py b/mercurial/dagparser.py
--- a/mercurial/dagparser.py
+++ b/mercurial/dagparser.py
@@ -219,7 +219,7 @@ def parsedag(desc):
                 yield 'n', (r, [p1])
                 p1 = r
                 r += 1
-        elif c == '*' or c == '/':
+        elif c in '*/':
             if c == '*':
                 c = nextch()
             c, pref = nextstring(c)
diff --git a/mercurial/dirstate.py b/mercurial/dirstate.py
--- a/mercurial/dirstate.py
+++ b/mercurial/dirstate.py
@@ -531,7 +531,7 @@ class dirstate(object):
                     match.dir(nf)
                     if not dirignore(nf):
                         wadd(nf)
-                elif kind == regkind or kind == lnkkind:
+                elif kind in (regkind, lnkkind):
                     results[nf] = st
                 else:
                     badfn(ff, badtype(kind))
diff --git a/mercurial/help.py b/mercurial/help.py
--- a/mercurial/help.py
+++ b/mercurial/help.py
@@ -25,7 +25,7 @@ def moduledoc(file):
             break
 
     start = line[:3]
-    if start == '"""' or start == "'''":
+    if start in ('"""', "'''"):
         line = line[3:]
         while line:
             if line.rstrip().endswith(start):
diff --git a/mercurial/merge.py b/mercurial/merge.py
--- a/mercurial/merge.py
+++ b/mercurial/merge.py
@@ -496,7 +496,7 @@ def update(repo, node, branchmerge, forc
                 raise util.Abort(_("outstanding uncommitted changes "
                                    "(use 'hg status' to list changes)"))
         elif not overwrite:
-            if pa == p1 or pa == p2: # linear
+            if pa in (p1, p2): # linear
                 pass # all good
             elif wc.files() or wc.deleted():
                 raise util.Abort(_("crosses branches (use 'hg merge' to merge "
diff --git a/mercurial/pure/diffhelpers.py b/mercurial/pure/diffhelpers.py
--- a/mercurial/pure/diffhelpers.py
+++ b/mercurial/pure/diffhelpers.py
@@ -41,9 +41,9 @@ def fix_newline(hunk, a, b):
         hline = l[:-1]
     c = hline[0]
 
-    if c == " " or c == "+":
+    if c in " +":
         b[-1] = hline[1:]
-    if c == " " or c == "-":
+    if c in " -":
         a[-1] = hline
     hunk[-1] = hline
     return 0
diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -87,7 +87,7 @@ def tokenize(program):
 # helpers
 
 def getstring(x, err):
-    if x and (x[0] == 'string' or x[0] == 'symbol'):
+    if x and x[0] in ('string', 'symbol'):
         return x[1]
     raise error.ParseError(err)
 
@@ -537,7 +537,7 @@ def optimize(x, small):
                          '-' + getstring(x[1], _("can't negate that"))), small)
     elif op in 'string symbol negate':
         return smallbonus, x # single revisions are small
-    elif op == 'and' or op == 'dagrange':
+    elif op in ('and', 'dagrange'):
         wa, ta = optimize(x[1], True)
         wb, tb = optimize(x[2], True)
         w = min(wa, wb)
diff --git a/mercurial/simplemerge.py b/mercurial/simplemerge.py
--- a/mercurial/simplemerge.py
+++ b/mercurial/simplemerge.py
@@ -110,7 +110,7 @@ class Merge3Text(object):
             if what == 'unchanged':
                 for i in range(t[1], t[2]):
                     yield self.base[i]
-            elif what == 'a' or what == 'same':
+            elif what in ('a', 'same'):
                 for i in range(t[1], t[2]):
                     yield self.a[i]
             elif what == 'b':
@@ -142,7 +142,7 @@ class Merge3Text(object):
             if what == 'unchanged':
                 for i in range(t[1], t[2]):
                     yield 'u | ' + self.base[i]
-            elif what == 'a' or what == 'same':
+            elif what in ('a', 'same'):
                 for i in range(t[1], t[2]):
                     yield what[0] + ' | ' + self.a[i]
             elif what == 'b':
@@ -181,7 +181,7 @@ class Merge3Text(object):
             what = t[0]
             if what == 'unchanged':
                 yield what, self.base[t[1]:t[2]]
-            elif what == 'a' or what == 'same':
+            elif what in ('a', 'same'):
                 yield what, self.a[t[1]:t[2]]
             elif what == 'b':
                 yield what, self.b[t[1]:t[2]]
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -640,7 +640,7 @@ def fspath(name, root):
     # If name is absolute, make it relative
     if name.lower().startswith(root.lower()):
         l = len(root)
-        if name[l] == os.sep or name[l] == os.altsep:
+        if name[l] in (os.sep, os.altsep):
             l = l + 1
         name = name[l:]
 
@@ -1008,7 +1008,7 @@ def strdate(string, format, defaults=[])
             hours = int(tz[1:3])
             minutes = int(tz[3:5])
             return -sign * (hours * 60 + minutes) * 60
-        if tz == "GMT" or tz == "UTC":
+        if tz in ("GMT", "UTC"):
             return 0
         return None
 
diff --git a/mercurial/win32.py b/mercurial/win32.py
--- a/mercurial/win32.py
+++ b/mercurial/win32.py
@@ -50,7 +50,7 @@ def nlinks(pathname):
         if not dirname:
             dirname = '.'
         dt = win32file.GetDriveType(dirname + '\\')
-        if dt == 4 or dt == 1:
+        if dt in (4, 1):
             # Fake hardlink to force COW for network drives
             links = 2
     return links