diff --git a/py/objfloat.c b/py/objfloat.c
index 9d7b796895..268bc2bde5 100644
--- a/py/objfloat.c
+++ b/py/objfloat.c
@@ -8,6 +8,7 @@
 #include "mpconfig.h"
 #include "qstr.h"
 #include "obj.h"
+#include "parsenum.h"
 #include "runtime0.h"
 
 #if MICROPY_ENABLE_FLOAT
@@ -32,8 +33,12 @@ STATIC mp_obj_t float_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const m
             return mp_obj_new_float(0);
 
         case 1:
-            // TODO allow string as arg and parse it
-            if (MP_OBJ_IS_TYPE(args[0], &float_type)) {
+            if (MP_OBJ_IS_STR(args[0])) {
+                // a string, parse it
+                uint l;
+                const char *s = mp_obj_str_get_data(args[0], &l);
+                return mp_parse_num_decimal(s, l);
+            } else if (MP_OBJ_IS_TYPE(args[0], &float_type)) {
                 return args[0];
             } else {
                 return mp_obj_new_float(mp_obj_get_float(args[0]));
diff --git a/py/objint.c b/py/objint.c
index 82bab9ea18..0caaab649b 100644
--- a/py/objint.c
+++ b/py/objint.c
@@ -5,10 +5,10 @@
 
 #include "nlr.h"
 #include "misc.h"
-#include "strtonum.h"
 #include "mpconfig.h"
 #include "qstr.h"
 #include "obj.h"
+#include "parsenum.h"
 #include "objint.h"
 
 // This dispatcher function is expected to be independent of the implementation
@@ -25,7 +25,7 @@ STATIC mp_obj_t int_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp_
                 // a string, parse it
                 uint l;
                 const char *s = mp_obj_str_get_data(args[0], &l);
-                return MP_OBJ_NEW_SMALL_INT(mp_strtonum(s, 0));
+                return mp_parse_num_integer(s, l, 0);
             } else {
                 return MP_OBJ_NEW_SMALL_INT(mp_obj_get_int(args[0]));
             }
@@ -36,7 +36,7 @@ STATIC mp_obj_t int_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp_
             // TODO proper error checking of argument types
             uint l;
             const char *s = mp_obj_str_get_data(args[0], &l);
-            return MP_OBJ_NEW_SMALL_INT(mp_strtonum(s, mp_obj_get_int(args[1])));
+            return mp_parse_num_integer(s, l, mp_obj_get_int(args[1]));
         }
 
         default:
diff --git a/py/parse.h b/py/parse.h
index 6492f4d9e0..135de47d13 100644
--- a/py/parse.h
+++ b/py/parse.h
@@ -8,7 +8,7 @@ struct _mp_lexer_t;
 //  - xx...x00110: an integer; bits 5 and above are the qstr holding the value
 //  - xx...x01010: a decimal; bits 5 and above are the qstr holding the value
 //  - xx...x01110: a string; bits 5 and above are the qstr holding the value
-//  - xx...x10010: a string with triple quotes; bits 5 and above are the qstr holding the value
+//  - xx...x10010: a string of bytes; bits 5 and above are the qstr holding the value
 //  - xx...x10110: a token; bits 5 and above are mp_token_kind_t
 
 // TODO: these can now be unified with MP_OBJ_FITS_SMALL_INT(x)
diff --git a/py/parsenum.c b/py/parsenum.c
new file mode 100644
index 0000000000..64594cd1b4
--- /dev/null
+++ b/py/parsenum.c
@@ -0,0 +1,169 @@
+#include <stdlib.h>
+
+#include "misc.h"
+#include "mpconfig.h"
+#include "qstr.h"
+#include "nlr.h"
+#include "obj.h"
+#include "parsenum.h"
+
+#if defined(UNIX)
+
+#include <ctype.h>
+#include <errno.h>
+
+mp_obj_t mp_parse_num_integer(const char *restrict str, uint len, int base) {
+    // TODO at the moment we ignore len; we should honour it!
+    // TODO detect integer overflow and return bignum
+
+    int c, neg = 0;
+    const char *p = str;
+    char *num;
+    long found;
+
+    // check radix base
+    if ((base != 0 && base < 2) || base > 36) {
+        nlr_jump(mp_obj_new_exception_msg(&mp_type_ValueError, "ValueError: int() arg 2 must be >=2 and <= 36"));
+    }
+    // skip surrounded whitespace
+    while (isspace((c = *(p++))));
+    if (c == 0) {
+        goto value_error;
+    }
+    // preced sign
+    if (c == '+' || c == '-') {
+        neg = - (c == '-');
+        c = *(p++);
+    }
+
+    // find real radix base, and strip preced '0x', '0o' and '0b'
+    // TODO somehow merge with similar code in parse.c
+    if ((base == 0 || base == 16) && c == '0') {
+        c = *(p++);
+        if ((c | 32) == 'x') {
+            base = 16;
+        } else if (base == 0 && (c | 32) == 'o') {
+            base = 8;
+        } else if (base == 0 && (c | 32) == 'b') {
+            base = 2;
+        } else {
+            base = 10;
+            p -= 2;
+        }
+    } else if (base == 8 && c == '0') {
+        c = *(p++);
+        if ((c | 32) != 'o') {
+            p -= 2;
+        }
+    } else if (base == 2 && c == '0') {
+        c = *(p++);
+        if ((c | 32) != 'b') {
+            p -= 2;
+        }
+    } else {
+        if (base == 0) base = 10;
+        p--;
+    }
+
+    errno = 0;
+    found = strtol(p, &num, base);
+    if (errno) {
+        goto value_error;
+    } else if (found && *(num) == 0) {
+        goto done;
+    } else if (found || num != p) {
+        goto check_tail_space;
+    } else {
+        goto value_error;
+    }
+
+check_tail_space:
+    if (*(num) != 0) {
+        while (isspace((c = *(num++))));
+        if (c != 0) {
+            goto value_error;
+        }
+    }
+
+done:
+    return MP_OBJ_NEW_SMALL_INT((found ^ neg) - neg);
+
+value_error:
+    nlr_jump(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "invalid literal for int() with base %d: '%s'", base, str));
+}
+
+#else /* defined(UNIX) */
+
+mp_obj_t mp_parse_num_integer(const char *restrict str, uint len, int base) {
+    // TODO port strtol to stm
+    return MP_OBJ_NEW_SMALL_INT(0);
+}
+
+#endif /* defined(UNIX) */
+
+#define PARSE_DEC_IN_INTG (1)
+#define PARSE_DEC_IN_FRAC (2)
+#define PARSE_DEC_IN_EXP  (3)
+
+mp_obj_t mp_parse_num_decimal(const char *str, uint len) {
+#if MICROPY_ENABLE_FLOAT
+    int in = PARSE_DEC_IN_INTG;
+    mp_float_t dec_val = 0;
+    bool exp_neg = false;
+    int exp_val = 0;
+    int exp_extra = 0;
+    bool imag = false;
+    const char *top = str + len;
+    for (; str < top; str++) {
+        int dig = *str;
+        if ('0' <= dig && dig <= '9') {
+            dig -= '0';
+            if (in == PARSE_DEC_IN_EXP) {
+                exp_val = 10 * exp_val + dig;
+            } else {
+                dec_val = 10 * dec_val + dig;
+                if (in == PARSE_DEC_IN_FRAC) {
+                    exp_extra -= 1;
+                }
+            }
+        } else if (in == PARSE_DEC_IN_INTG && dig == '.') {
+            in = PARSE_DEC_IN_FRAC;
+        } else if (in != PARSE_DEC_IN_EXP && (dig == 'E' || dig == 'e')) {
+            in = PARSE_DEC_IN_EXP;
+            if (str[1] == '+') {
+                str++;
+            } else if (str[1] == '-') {
+                str++;
+                exp_neg = true;
+            }
+        } else if (dig == 'J' || dig == 'j') {
+            str++;
+            imag = true;
+            break;
+        } else {
+            // unknown character
+            break;
+        }
+    }
+    if (*str != 0) {
+        nlr_jump(mp_obj_new_exception_msg(&mp_type_SyntaxError, "invalid syntax for number"));
+    }
+    if (exp_neg) {
+        exp_val = -exp_val;
+    }
+    exp_val += exp_extra;
+    for (; exp_val > 0; exp_val--) {
+        dec_val *= 10;
+    }
+    for (; exp_val < 0; exp_val++) {
+        dec_val *= 0.1;
+    }
+    if (imag) {
+        return mp_obj_new_complex(0, dec_val);
+    } else {
+        return mp_obj_new_float(dec_val);
+    }
+#else
+    nlr_jump(mp_obj_new_exception_msg(&mp_type_SyntaxError, "decimal numbers not supported"));
+#endif
+}
diff --git a/py/parsenum.h b/py/parsenum.h
new file mode 100644
index 0000000000..5a2e42da50
--- /dev/null
+++ b/py/parsenum.h
@@ -0,0 +1,2 @@
+mp_obj_t mp_parse_num_integer(const char *restrict str, uint len, int base);
+mp_obj_t mp_parse_num_decimal(const char *str, uint len);
diff --git a/py/py.mk b/py/py.mk
index cbb63b4bfc..199c3aadc8 100644
--- a/py/py.mk
+++ b/py/py.mk
@@ -31,9 +31,9 @@ PY_O_BASENAME = \
 	asmthumb.o \
 	emitnthumb.o \
 	emitinlinethumb.o \
+	parsenum.o \
 	runtime.o \
 	map.o \
-	strtonum.o \
 	obj.o \
 	objarray.o \
 	objbool.o \
diff --git a/py/runtime.c b/py/runtime.c
index b08ae3d4e7..20bfa0b20f 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -13,6 +13,7 @@
 #include "mpconfig.h"
 #include "qstr.h"
 #include "obj.h"
+#include "parsenum.h"
 #include "runtime0.h"
 #include "runtime.h"
 #include "map.h"
@@ -371,72 +372,11 @@ mp_obj_t rt_list_append(mp_obj_t self_in, mp_obj_t arg) {
     return mp_obj_list_append(self_in, arg);
 }
 
-#define PARSE_DEC_IN_INTG (1)
-#define PARSE_DEC_IN_FRAC (2)
-#define PARSE_DEC_IN_EXP  (3)
-
 mp_obj_t rt_load_const_dec(qstr qstr) {
-#if MICROPY_ENABLE_FLOAT
     DEBUG_OP_printf("load '%s'\n", qstr_str(qstr));
-    const char *s = qstr_str(qstr);
-    int in = PARSE_DEC_IN_INTG;
-    mp_float_t dec_val = 0;
-    bool exp_neg = false;
-    int exp_val = 0;
-    int exp_extra = 0;
-    bool imag = false;
-    for (; *s; s++) {
-        int dig = *s;
-        if ('0' <= dig && dig <= '9') {
-            dig -= '0';
-            if (in == PARSE_DEC_IN_EXP) {
-                exp_val = 10 * exp_val + dig;
-            } else {
-                dec_val = 10 * dec_val + dig;
-                if (in == PARSE_DEC_IN_FRAC) {
-                    exp_extra -= 1;
-                }
-            }
-        } else if (in == PARSE_DEC_IN_INTG && dig == '.') {
-            in = PARSE_DEC_IN_FRAC;
-        } else if (in != PARSE_DEC_IN_EXP && (dig == 'E' || dig == 'e')) {
-            in = PARSE_DEC_IN_EXP;
-            if (s[1] == '+') {
-                s++;
-            } else if (s[1] == '-') {
-                s++;
-                exp_neg = true;
-            }
-        } else if (dig == 'J' || dig == 'j') {
-            s++;
-            imag = true;
-            break;
-        } else {
-            // unknown character
-            break;
-        }
-    }
-    if (*s != 0) {
-        nlr_jump(mp_obj_new_exception_msg(&mp_type_SyntaxError, "invalid syntax for number"));
-    }
-    if (exp_neg) {
-        exp_val = -exp_val;
-    }
-    exp_val += exp_extra;
-    for (; exp_val > 0; exp_val--) {
-        dec_val *= 10;
-    }
-    for (; exp_val < 0; exp_val++) {
-        dec_val *= 0.1;
-    }
-    if (imag) {
-        return mp_obj_new_complex(0, dec_val);
-    } else {
-        return mp_obj_new_float(dec_val);
-    }
-#else
-    nlr_jump(mp_obj_new_exception_msg(&mp_type_SyntaxError, "decimal numbers not supported"));
-#endif
+    uint len;
+    const byte* data = qstr_data(qstr, &len);
+    return mp_parse_num_decimal((const char*)data, len);
 }
 
 mp_obj_t rt_load_const_str(qstr qstr) {
diff --git a/py/strtonum.c b/py/strtonum.c
deleted file mode 100644
index 4a62756512..0000000000
--- a/py/strtonum.c
+++ /dev/null
@@ -1,98 +0,0 @@
-#if defined(UNIX)
-
-#include <ctype.h>
-#include <errno.h>
-#include <stdlib.h>
-
-#include "misc.h"
-#include "strtonum.h"
-#include "mpconfig.h"
-#include "qstr.h"
-#include "nlr.h"
-#include "obj.h"
-
-long mp_strtonum(const char *restrict s, int base) {
-    int c, neg = 0;
-    const char *p = s;
-    char *num;
-    long found;
-
-    // check radix base
-    if ((base != 0 && base < 2) || base > 36) {
-        nlr_jump(mp_obj_new_exception_msg(&mp_type_ValueError, "ValueError: int() arg 2 must be >=2 and <= 36"));
-    }
-    // skip surrounded whitespace
-    while (isspace((c = *(p++))));
-    if (c == 0) {
-        goto value_error;
-    }
-    // preced sign
-    if (c == '+' || c == '-') {
-        neg = - (c == '-');
-        c = *(p++);
-    }
-
-    // find real radix base, and strip preced '0x', '0o' and '0b'
-    // TODO somehow merge with similar code in parse.c
-    if ((base == 0 || base == 16) && c == '0') {
-        c = *(p++);
-        if ((c | 32) == 'x') {
-            base = 16;
-        } else if (base == 0 && (c | 32) == 'o') {
-            base = 8;
-        } else if (base == 0 && (c | 32) == 'b') {
-            base = 2;
-        } else {
-            base = 10;
-            p -= 2;
-        }
-    } else if (base == 8 && c == '0') {
-        c = *(p++);
-        if ((c | 32) != 'o') {
-            p -= 2;
-        }
-    } else if (base == 2 && c == '0') {
-        c = *(p++);
-        if ((c | 32) != 'b') {
-            p -= 2;
-        }
-    } else {
-        if (base == 0) base = 10;
-        p--;
-    }
-
-    errno = 0;
-    found = strtol(p, &num, base);
-    if (errno) {
-        goto value_error;
-    } else if (found && *(num) == 0) {
-        goto done;
-    } else if (found || num != p) {
-        goto check_tail_space;
-    } else {
-        goto value_error;
-    }
-
-check_tail_space:
-    if (*(num) != 0) {
-        while (isspace((c = *(num++))));
-        if (c != 0) {
-            goto value_error;
-        }
-    }
-
-done:
-    return (found ^ neg) - neg;
-
-value_error:
-    nlr_jump(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "invalid literal for int() with base %d: '%s'", base, s));
-}
-
-#else /* defined(UNIX) */
-
-long mp_strtonum(const char *restrict s, int base) {
-    // TODO port strtol to stm
-    return 0;
-}
-
-#endif /* defined(UNIX) */
diff --git a/py/strtonum.h b/py/strtonum.h
deleted file mode 100644
index 10b6732edb..0000000000
--- a/py/strtonum.h
+++ /dev/null
@@ -1 +0,0 @@
-long mp_strtonum(const char *restrict s, int base);