Class Formatter

Lib/dis.py:441–553

class Formatter:

    def __init__(self, file=None, lineno_width=0, offset_width=0, label_width=0,
                 line_offset=0, show_caches=False, *, show_positions=False):
        """Create a Formatter

        *file* where to write the output
        *lineno_width* sets the width of the source location field (0 omits it).
        Should be large enough for a line number or full positions (depending
        on the value of *show_positions*).
        *offset_width* sets the width of the instruction offset field
        *label_width* sets the width of the label field
        *show_caches* is a boolean indicating whether to display cache lines
        *show_positions* is a boolean indicating whether full positions should
        be reported instead of only the line numbers.
        """
        self.file = file
        self.lineno_width = lineno_width
        self.offset_width = offset_width
        self.label_width = label_width
        self.show_caches = show_caches
        self.show_positions = show_positions

    def print_instruction(self, instr, mark_as_current=False):
        self.print_instruction_line(instr, mark_as_current)
        if self.show_caches and instr.cache_info:
            offset = instr.offset
            for name, size, data in instr.cache_info:
                for i in range(size):
                    offset += 2
                    # Only show the fancy argrepr for a CACHE instruction when it's
                    # the first entry for a particular cache value:
                    if i == 0:
                        argrepr = f"{name}: {int.from_bytes(data, sys.byteorder)}"
                    else:
                        argrepr = ""
                    self.print_instruction_line(
                        Instruction("CACHE", CACHE, 0, None, argrepr, offset, offset,
                                    False, None, None, instr.positions),
                        False)

    def print_instruction_line(self, instr, mark_as_current):
        """Format instruction details for inclusion in disassembly output."""
        lineno_width = self.lineno_width
        offset_width = self.offset_width
        label_width = self.label_width

        new_source_line = (lineno_width > 0 and
                           instr.starts_line and
                           instr.offset > 0)
        if new_source_line:
            print(file=self.file)

        fields = []
        # Column: Source code locations information
        if lineno_width:
            if self.show_positions:
                # reporting positions instead of just line numbers