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Copy in py-eval from swift-e-lab
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‎work/py-eval/.gitignore‎

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py-eval
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*.o

‎work/py-eval/Makefile‎

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# Edit Python settings here
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# PYTHON_HOME = ${HOME}/sfw/Python-2.7.10
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# PYTHON_VERSION_MAJOR = 2
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# PYTHON_VERSION_MINOR = 7
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# PYTHON_VERSION_SUFFIX =
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PYTHON_HOME = ${HOME}/sfw/Python-3.6.1
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PYTHON_VERSION_MAJOR = 3
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PYTHON_VERSION_MINOR = 6
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PYTHON_VERSION_SUFFIX = m
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# End Python settings
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PYTHON_VERSION = $(PYTHON_VERSION_MAJOR).$(PYTHON_VERSION_MINOR)$(PYTHON_VERSION_SUFFIX)
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INCLUDES = -I $(PYTHON_HOME)/include/python$(PYTHON_VERSION)
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LIBS = -L $(PYTHON_HOME)/lib -lpython$(PYTHON_VERSION)
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RPATHS = -Wl,-rpath -Wl,$(PYTHON_HOME)/lib
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CFLAGS = -g -Wall -O0 -fPIC -DPYTHON_VERSION_MAJOR=$(PYTHON_VERSION_MAJOR) $(INCLUDES) -fdiagnostics-color=always
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SRCS = main.c py-eval.c io.c
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OBJS = $(patsubst %.c,%.o,$(SRCS))
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all: py-eval
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$(OBJS): Makefile # Rebuild everything if Makefile changes
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py-eval: $(OBJS)
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gcc -fPIC -o $(@) $(OBJS) \
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$(LIBS) \
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$(RPATHS)
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clean:
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@ rm -fv $(OBJS) py-eval

‎work/py-eval/README.adoc‎

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= Simple C-Python Example
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The program is called py-eval. Its arguments are:
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1. Zero or more Python scripts that are executed with no return value.
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2. Any number of hyphen tokens - , which provides a _New Python Interpreter_ at each point.
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2. Exactly one Python script that returns a string.
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This has been tested with Python 2.7.10 and Python 3.6m.
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For more verbose output, set verbose=true in py-eval.c
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You may need to set environment variable PYTHONHOME at runtime to agree with PYTHON_HOME in the Makefile.
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Transcript:
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----
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# edit Makefile for Python installation settings
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make
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export PYTHONHOME=...
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./py-eval py/import-io.py py/hello.py
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----
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To test the exception handling capabilities, do:
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----
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./py-eval py/err.py py/hello.py
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----
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To test the _New Python Interpreter_ feature, compare:
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----
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cd py
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../py-eval x2.py print_x.py hello.py
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2
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'Hello'
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----
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with the same thing with added - :
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----
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cd py
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../py-eval x2.py - print_x.py hello.py
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PYTHON EXCEPTION:
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<class 'NameError'>
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name 'x' is not defined
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py-eval: python code failed.
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----

‎work/py-eval/io.c‎

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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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char*
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slurp(const char* filename)
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{
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FILE* file = fopen(filename, "r");
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if (file == NULL)
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{
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printf("slurp(): could not read from: %s\n", filename);
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return NULL;
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}
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struct stat s;
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int rc = stat(filename, &s);
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if (rc != 0)
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{
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printf("slurp(): could not stat: %s\n", filename);
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return NULL;
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}
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size_t length = s.st_size;
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char* result = malloc(length+1);
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if (result == NULL)
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{
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printf("slurp(): could not allocate memory for: %s\n", filename);
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return NULL;
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}
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char* p = result;
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size_t actual = fread(p, sizeof(char), length, file);
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if (actual != length)
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{
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printf("could not read all %zi bytes from file: %s\n",
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length, filename);
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free(result);
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return NULL;
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}
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result[length] = '\0';
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fclose(file);
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return result;
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}
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void
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chomp(char* s)
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{
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size_t length = strlen(s);
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if (s[length-1] == '\n')
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s[length-1] = '\0';
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}

‎work/py-eval/io.h‎

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#pragma once
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char* slurp(const char* filename);
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void chomp(char* s);

‎work/py-eval/main.c‎

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#include <stdarg.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "io.h"
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#include "py-eval.h"
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char* usage =
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"usage: py-eval [code_files]* expr_file\n"
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"use - to reset the interpreter\n"
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"see the README\n";
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static void crash(char* fmt, ...);
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static void do_python_code(char* code_file);
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static void do_python_eval(char* expr_file);
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int
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main(int argc, char* argv[])
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{
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if (argc == 1) crash(usage);
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python_init();
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int cf; // current file
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for (cf = 1; cf < argc-1; cf++)
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{
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char* code_file = argv[cf];
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if (strcmp(code_file, "-") == 0)
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{
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python_reset();
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continue;
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}
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do_python_code(code_file);
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}
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do_python_eval(argv[cf]);
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// Clean up
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python_finalize();
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exit(EXIT_SUCCESS);
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}
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static void
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do_python_code(char* code_file)
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{
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char* code = slurp(code_file);
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chomp(code);
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if (code == NULL) crash("failed to read: %s", code_file);
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bool rc = python_code(code);
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free(code);
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if (!rc) crash("python code failed.");
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}
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static void
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do_python_eval(char* expr_file)
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{
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// Read Python expr file
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if (strcmp(expr_file, "-") == 0)
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crash("expr file cannot be -");
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char* expr = slurp(expr_file);
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if (expr == NULL) crash("failed to read: %s", expr_file);
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chomp(expr);
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// Do Python eval
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char* result;
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bool rc = python_eval(expr, &result);
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free(expr);
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if (!rc) crash("python expr failed.");
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printf("%s\n", result);
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}
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static void
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crash(char* fmt, ...)
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{
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printf("py-eval: ");
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va_list ap;
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va_start(ap, fmt);
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vprintf(fmt, ap);
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va_end(ap);
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printf("\n");
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exit(EXIT_FAILURE);
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}

‎work/py-eval/py-eval.c‎

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#include <Python.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include "py-eval.h"
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static void
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verbose(char* fmt, ...)
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{
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static bool verbose = false;
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if (!verbose) return;
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va_list ap;
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va_start(ap, fmt);
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vprintf(fmt, ap);
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printf("\n");
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va_end(ap);
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}
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static bool
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handle_python_exception(void)
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{
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printf("\n");
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printf("PYTHON EXCEPTION:\n");
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#if PYTHON_VERSION_MAJOR >= 3
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PyObject *exc,*val,*tb;
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PyErr_Fetch(&exc,&val,&tb);
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PyObject_Print(exc, stdout, Py_PRINT_RAW);
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printf("\n");
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PyObject_Print(val, stdout, Py_PRINT_RAW);
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printf("\n");
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#else // Python 2
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PyErr_Print();
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#endif
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return false;
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}
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static bool
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handle_python_non_string(PyObject* o)
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{
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printf("python: expression did not return a string!\n");
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fflush(stdout);
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printf("python: expression evaluated to: ");
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PyObject_Print(o, stdout, 0);
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printf("\n");
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return false;
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}
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static PyObject* main_module = NULL;
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static PyObject* main_dict = NULL;
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static PyObject* local_dict = NULL;
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static bool initialized = false;
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bool
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python_init()
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{
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if (initialized) return true;
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verbose("python: initializing...");
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Py_InitializeEx(1);
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main_module = PyImport_AddModule("__main__");
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if (main_module == NULL) return handle_python_exception();
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main_dict = PyModule_GetDict(main_module);
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if (main_dict == NULL) return handle_python_exception();
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local_dict = PyDict_New();
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if (local_dict == NULL) return handle_python_exception();
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initialized = true;
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return true;
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}
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static char* python_result_default = "NOTHING";
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/**
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@param persist: If true, retain the Python interpreter,
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else finalize it
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@param code: The multiline string of Python code.
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@return true on success, false on error
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*/
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bool
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python_code(const char* code)
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{
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// Execute code:
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verbose("python: code: %s", code);
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PyRun_String(code, Py_file_input, main_dict, local_dict);
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if (PyErr_Occurred()) return handle_python_exception();
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return true;
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}
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/**
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The expr is evaluated to the returned result
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@param output: Store result pointer here
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*/
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bool python_eval(const char* expr, char** output)
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{
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char* result = python_result_default;
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// Evaluate expression:
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verbose("python: expr: %s", expr);
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PyObject* o = PyRun_String(expr, Py_eval_input, main_dict, local_dict);
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if (o == NULL) return handle_python_exception();
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// Convert Python result to C string
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int pc = PyArg_Parse(o, "s", &result);
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if (pc != 1) return handle_python_non_string(o);
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verbose("python: result: %s\n", result);
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*output = strdup(result);
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// Clean up and return:
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Py_DECREF(o);
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return true;
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}
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bool
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python_reset()
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{
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python_finalize();
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return python_init();
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}
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void
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python_finalize()
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{
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Py_Finalize();
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initialized = false;
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}

‎work/py-eval/py-eval.h‎

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#pragma once
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#include <stdbool.h>
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bool python_init(void);
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bool python_reset(void);
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bool python_code(const char* code);
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bool python_eval(const char* expression, char** output);
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void python_finalize(void);

‎work/py-eval/py/err.py‎

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‎work/py-eval/py/hello.py‎

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repr("Hello")

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