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py/objstr: For str.format, add nested/computed fields support. 

Eg: '{:{}}'.format(123, '>20')

@pohmelie was the original author of this patch, but @dpgeorge made
significant changes to reduce code size and improve efficiency.
pull/1810/merge
pohmelie 9 years ago
committed by Damien George
parent
2bd758fe96
commit
e3a29de1dc
2 changed files with 42 additions and 19 deletions
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  1. 53
      py/objstr.c
  2. 8
      tests/basics/string_format.py

53
py/objstr.c
View File

@ -34,6 +34,7 @@
#include "py/objlist.h"
#include "py/runtime0.h"
#include "py/runtime.h"
#include "py/stackctrl.h"
STATIC mp_obj_t str_modulo_format(mp_obj_t pattern, mp_uint_t n_args, const mp_obj_t *args, mp_obj_t dict);
@ -848,16 +849,12 @@ STATIC NORETURN void terse_str_format_value_error(void) {
nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "bad format string"));
}
mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs) {
assert(MP_OBJ_IS_STR_OR_BYTES(args[0]));
GET_STR_DATA_LEN(args[0], str, len);
int arg_i = 0;
vstr_t mp_obj_str_format_helper(const char *str, const char *top, int *arg_i, mp_uint_t n_args, const mp_obj_t *args, mp_map_t *kwargs) {
vstr_t vstr;
mp_print_t print;
vstr_init_print(&vstr, 16, &print);
for (const byte *top = str + len; str < top; str++) {
for (; str < top; str++) {
if (*str == '}') {
str++;
if (str < top && *str == '}') {
@ -886,7 +883,7 @@ mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs
vstr_t *field_name = NULL;
char conversion = '\0';
vstr_t *format_spec = NULL;
const char *format_spec = NULL;
if (str < top && *str != '}' && *str != '!' && *str != ':') {
field_name = vstr_new();
@ -927,9 +924,16 @@ mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs
// '{:d}'.format(True) returns '1'
// So we treat {:} as {} and this later gets treated to be {!s}
if (*str != '}') {
format_spec = vstr_new();
while (str < top && *str != '}') {
vstr_add_byte(format_spec, *str++);
format_spec = str;
for (int nest = 1; str < top;) {
if (*str == '{') {
++nest;
} else if (*str == '}') {
if (--nest == 0) {
break;
}
}
++str;
}
}
}
@ -957,7 +961,7 @@ mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs
const char *field = vstr_null_terminated_str(field_name);
const char *lookup = NULL;
if (MP_LIKELY(unichar_isdigit(*field))) {
if (arg_i > 0) {
if (*arg_i > 0) {
if (MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE) {
terse_str_format_value_error();
} else {
@ -970,7 +974,7 @@ mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs
nlr_raise(mp_obj_new_exception_msg(&mp_type_IndexError, "tuple index out of range"));
}
arg = args[index + 1];
arg_i = -1;
*arg_i = -1;
} else {
for (lookup = field; *lookup && *lookup != '.' && *lookup != '['; lookup++);
mp_obj_t field_q = mp_obj_new_str(field, lookup - field, true/*?*/);
@ -986,7 +990,7 @@ mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs
vstr_free(field_name);
field_name = NULL;
} else {
if (arg_i < 0) {
if (*arg_i < 0) {
if (MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE) {
terse_str_format_value_error();
} else {
@ -994,11 +998,11 @@ mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs
"can't switch from manual field specification to automatic field numbering"));
}
}
if ((uint)arg_i >= n_args - 1) {
if ((uint)*arg_i >= n_args - 1) {
nlr_raise(mp_obj_new_exception_msg(&mp_type_IndexError, "tuple index out of range"));
}
arg = args[arg_i + 1];
arg_i++;
arg = args[(*arg_i) + 1];
(*arg_i)++;
}
if (!format_spec && !conversion) {
conversion = 's';
@ -1037,7 +1041,10 @@ mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs
// precision ::= integer
// type ::= "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"
const char *s = vstr_null_terminated_str(format_spec);
// recursively call the formatter to format any nested specifiers
MP_STACK_CHECK();
vstr_t format_spec_vstr = mp_obj_str_format_helper(format_spec, str, arg_i, n_args, args, kwargs);
const char *s = vstr_null_terminated_str(&format_spec_vstr);
if (isalignment(*s)) {
align = *s++;
} else if (*s && isalignment(s[1])) {
@ -1084,8 +1091,7 @@ mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs
"invalid format specifier"));
}
}
vstr_free(format_spec);
format_spec = NULL;
vstr_clear(&format_spec_vstr);
}
if (!align) {
if (arg_looks_numeric(arg)) {
@ -1288,6 +1294,15 @@ mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs
}
}
return vstr;
}
mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs) {
assert(MP_OBJ_IS_STR_OR_BYTES(args[0]));
GET_STR_DATA_LEN(args[0], str, len);
int arg_i = 0;
vstr_t vstr = mp_obj_str_format_helper((const char*)str, (const char*)str + len, &arg_i, n_args, args, kwargs);
return mp_obj_new_str_from_vstr(&mp_type_str, &vstr);
}

8
tests/basics/string_format.py
View File

@ -66,6 +66,14 @@ test("{:>20}", "foo")
test("{:^20}", "foo")
test("{:<20}", "foo")
# nested format specifiers
print("{:{}}".format(123, '#>10'))
print("{:{}{}{}}".format(123, '#', '>', '10'))
print("{0:{1}{2}}".format(123, '#>', '10'))
print("{text:{align}{width}}".format(text="foo", align="<", width=20))
print("{text:{align}{width}}".format(text="foo", align="^", width=10))
print("{text:{align}{width}}".format(text="foo", align=">", width=30))
print("{foo}/foo".format(foo="bar"))
print("{}".format(123, foo="bar"))
print("{}-{foo}".format(123, foo="bar"))

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