"""
Representation and utils for ranges of PDF file pages.
Copyright (c) 2014, Steve Witham <switham_github@mac-guyver.com>.
All rights reserved. This software is available under a BSD license;
see https://github.com/py-pdf/pypdf/blob/main/LICENSE
"""
import re
from typing import Any, List, Tuple, Union
from .errors import ParseError
_INT_RE = r"(0|-?[1-9]\d*)" # A decimal int, don't allow "-0".
PAGE_RANGE_RE = f"^({_INT_RE}|({_INT_RE}?(:{_INT_RE}?(:{_INT_RE}?)?)))$"
# groups: 12 34 5 6 7 8
class PageRange:
"""
A slice-like representation of a range of page indices.
For example, page numbers, only starting at zero.
The syntax is like what you would put between brackets [ ].
The slice is one of the few Python types that can't be subclassed,
but this class converts to and from slices, and allows similar use.
- PageRange(str) parses a string representing a page range.
- PageRange(slice) directly "imports" a slice.
- to_slice() gives the equivalent slice.
- str() and repr() allow printing.
- indices(n) is like slice.indices(n).
"""
def __init__(self, arg: Union[slice, "PageRange", str]) -> None:
"""
Initialize with either a slice -- giving the equivalent page range,
or a PageRange object -- making a copy,
or a string like
"int", "[int]:[int]" or "[int]:[int]:[int]",
where the brackets indicate optional ints.
Remember, page indices start with zero.
Page range expression examples:
: all pages. -1 last page.
22 just the 23rd page. :-1 all but the last page.
0:3 the first three pages. -2 second-to-last page.
:3 the first three pages. -2: last two pages.
5: from the sixth page onward. -3:-1 third & second to last.
The third, "stride" or "step" number is also recognized.
::2 0 2 4 ... to the end. 3:0:-1 3 2 1 but not 0.
1:10:2 1 3 5 7 9 2::-1 2 1 0.
::-1 all pages in reverse order.
Note the difference between this notation and arguments to slice():
slice(3) means the first three pages;
PageRange("3") means the range of only the fourth page.
However PageRange(slice(3)) means the first three pages.
"""
if isinstance(arg, slice):
self._slice = arg
return
if isinstance(arg, PageRange):
self._slice = arg.to_slice()
return
m = isinstance(arg, str) and re.match(PAGE_RANGE_RE, arg)
if not m:
raise ParseError(arg)
elif m.group(2):
# Special case: just an int means a range of one page.
start = int(m.group(2))
stop = start + 1 if start != -1 else None
self._slice = slice(start, stop)
else:
self._slice = slice(*[int(g) if g else None for g in m.group(4, 6, 8)])
@staticmethod
def valid(input: Any) -> bool:
"""
True if input is a valid initializer for a PageRange.
Args:
input: A possible PageRange string or a PageRange object.
Returns:
True, if the ``input`` is a valid PageRange.
"""
return isinstance(input, (slice, PageRange)) or (
isinstance(input, str) and bool(re.match(PAGE_RANGE_RE, input))
)
def to_slice(self) -> slice:
"""Return the slice equivalent of this page range."""
return self._slice
def __str__(self) -> str:
"""A string like "1:2:3"."""
s = self._slice
indices: Union[Tuple[int, int], Tuple[int, int, int]]
if s.step is None:
if s.start is not None and s.stop == s.start + 1:
return str(s.start)
indices = s.start, s.stop
else:
indices = s.start, s.stop, s.step
return ":".join("" if i is None else str(i) for i in indices)
def __repr__(self) -> str:
"""A string like "PageRange('1:2:3')"."""
return "PageRange(" + repr(str(self)) + ")"
def indices(self, n: int) -> Tuple[int, int, int]:
"""
Assuming a sequence of length n, calculate the start and stop indices,
and the stride length of the PageRange.
See help(slice.indices).
Args:
n: the length of the list of pages to choose from.
Returns:
Arguments for range().
"""
return self._slice.indices(n)
def __eq__(self, other: object) -> bool:
if not isinstance(other, PageRange):
return False
return self._slice == other._slice
def __add__(self, other: "PageRange") -> "PageRange":
if not isinstance(other, PageRange):
raise TypeError(f"Can't add PageRange and {type(other)}")
if self._slice.step is not None or other._slice.step is not None:
raise ValueError("Can't add PageRange with stride")
a = self._slice.start, self._slice.stop
b = other._slice.start, other._slice.stop
if a[0] > b[0]:
a, b = b, a
# Now a[0] is the smallest
if b[0] > a[1]:
# There is a gap between a and b.
raise ValueError("Can't add PageRanges with gap")
return PageRange(slice(a[0], max(a[1], b[1])))
PAGE_RANGE_ALL = PageRange(":") # The range of all pages.
def parse_filename_page_ranges(
args: List[Union[str, PageRange, None]]
) -> List[Tuple[str, PageRange]]:
"""
Given a list of filenames and page ranges, return a list of (filename, page_range) pairs.
Args:
args: A list where the first element is a filename. The other elements are
filenames, page-range expressions, slice objects, or PageRange objects.
A filename not followed by a page range indicates all pages of the file.
Returns:
A list of (filename, page_range) pairs.
"""
pairs: List[Tuple[str, PageRange]] = []
pdf_filename = None
did_page_range = False
for arg in args + [None]:
if PageRange.valid(arg):
if not pdf_filename:
raise ValueError(
"The first argument must be a filename, not a page range."
)
pairs.append((pdf_filename, PageRange(arg)))
did_page_range = True
else:
# New filename or end of list--do all of the previous file?
if pdf_filename and not did_page_range:
pairs.append((pdf_filename, PAGE_RANGE_ALL))
pdf_filename = arg
did_page_range = False
return pairs
PageRangeSpec = Union[str, PageRange, Tuple[int, int], Tuple[int, int, int], List[int]]
