py: implement str.lower and str.upper

Updates #232

py/string.go

@@ -218,6 +218,14 @@ replaced.`)
 		return self.(String).LStrip(args)
 	}, 0, "lstrip(chars) -> replace chars from begining of string")
 
+	StringType.Dict["upper"] = MustNewMethod("upper", func(self Object, args Tuple, kwargs StringDict) (Object, error) {
+		return self.(String).Upper()
+	}, 0, "upper() -> a copy of the string converted to uppercase")
+
+	StringType.Dict["lower"] = MustNewMethod("lower", func(self Object, args Tuple, kwargs StringDict) (Object, error) {
+		return self.(String).Lower()
+	}, 0, "lower() -> a copy of the string converted to lowercase")
+
 }
 
 // Type of this object
@@ -739,6 +747,14 @@ func (s String) RStrip(args Tuple) (Object, error) {
 	return String(strings.TrimRightFunc(string(s), f)), nil
 }
 
+func (s String) Upper() (Object, error) {
+	return String(strings.ToUpper(string(s))), nil
+}
+
+func (s String) Lower() (Object, error) {
+	return String(strings.ToLower(string(s))), nil
+}
+
 // Check stringerface is satisfied
 var (
 	_ richComparison     = String("")

py/string_test.go

@@ -98,3 +98,49 @@ func TestStringFind(t *testing.T) {
 		})
 	}
 }
+
+func TestStringUpper(t *testing.T) {
+	tests := []struct {
+		name string
+		s    String
+		want Object
+	}{{
+		name: "abc",
+		s:    String("abc"),
+		want: String("ABC")},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := tt.s.Upper()
+			if err != nil {
+				t.Fatalf("Upper() error = %v", err)
+			}
+			if got.(String) != tt.want.(String) {
+				t.Fatalf("Upper() got = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestStringLower(t *testing.T) {
+	tests := []struct {
+		name string
+		s    String
+		want Object
+	}{{
+		name: "ABC",
+		s:    String("ABC"),
+		want: String("abc")},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := tt.s.Lower()
+			if err != nil {
+				t.Fatalf("Lower() error = %v", err)
+			}
+			if got.(String) != tt.want.(String) {
+				t.Fatalf("Lower() got = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

py/tests/string.py

@@ -897,6 +897,14 @@ def index(s, i):
 assert a.lstrip("a ") == "bada a"
 assert a.strip("a ") == "bad"
 
+doc="upper"
+a = "abc"
+assert a.upper() == "ABC"
+
+doc="lower"
+a = "ABC"
+assert a.lower() == "abc"
+
 class Index:
     def __index__(self):
         return 1