On Sunday, December 5, 2021 at 9:56:03 AM UTC-6 Edward K. Ream wrote:
> I have begun my study. I'll ask questions as needed.
I like to ask questions of the code :-) The split_root function defines
"body" as follows:
def body(a, b, tag):
return ''.join(lines[a-1:b and (b-1)])
The split_class function defines "body" this way:
def body(a, b, tag):
return ''.join(nlines[a-1:b and (b-1)])
Notice: "b and (b-1)" may evaluate to None. But lines[a:None] means
lines[a:]. I didn't know that None was a valid index!
For study purposes, I add traces to each:
def body(a, b, tag): # split_root.
lines2 = lines[a-1:b and (b-1)]
g.trace(f" split_root: lines: {len(lines2):<4} {a!r:>4}:{b and
(b-1)!r:<4} {tag}")
return ''.join(lines2)
def body(a, b, tag): # split_class
lines2 = nlines[a-1:b and (b-1)]
g.trace(f"split_class: lines: {len(lines2):<4} {a!r:>4}:{b and
(b-1)!r:<4} {tag}")
return ''.join(lines2)
Each call to these functions has a different tag (not shown).
These traces produce the following when importing difflib.py:
body split_root: lines: 0 1:0 head: Imported Files...
body split_root: lines: 0 2097:None tail: Imported Files...
body split_root: lines: 38 1:38 Declarations
body split_root: lines: 5 39:43 _calculate_ratio
body split_root: lines: 654 44:697 class SequenceMatcher
body split_class: lines: 107 1:107 class SequenceMatcher::Declarations
body split_class: lines: 64 108:171 class SequenceMatcher::__init__
body split_class: lines: 12 172:183 class SequenceMatcher::set_seqs
body split_class: lines: 26 184:209 class SequenceMatcher::set_seq1
body split_class: lines: 44 210:253 class SequenceMatcher::set_seq2
body split_class: lines: 39 254:292 class SequenceMatcher::__chain_b
body split_class: lines: 116 293:408 class
SequenceMatcher::find_longest_match
body split_class: lines: 71 409:479 class
SequenceMatcher::get_matching_blocks
body split_class: lines: 55 480:534 class SequenceMatcher::get_opcodes
body split_class: lines: 50 535:584 class
SequenceMatcher::get_grouped_opcodes
body split_class: lines: 25 585:609 class SequenceMatcher::ratio
body split_class: lines: 29 610:638 class SequenceMatcher::quick_ratio
body split_class: lines: 12 639:650 class
SequenceMatcher::real_quick_ratio
body split_root: lines: 49 698:746 get_close_matches
body split_root: lines: 9 747:755 _keep_original_ws
body split_root: lines: 327 756:1082 class Differ
body split_root: lines: 2 1083:1084 Declarations
body split_root: lines: 16 1085:1100 IS_LINE_JUNK
body split_root: lines: 23 1101:1123 IS_CHARACTER_JUNK
body split_root: lines: 11 1124:1134 _format_range_unified
body split_root: lines: 73 1135:1207 unified_diff
body split_root: lines: 12 1208:1219 _format_range_context
body split_root: lines: 76 1220:1295 context_diff
body split_root: lines: 17 1296:1312 _check_types
body split_root: lines: 30 1313:1342 diff_bytes
body split_root: lines: 37 1343:1379 ndiff
body split_root: lines: 270 1380:1649 _mdiff
body split_root: lines: 56 1650:1705 Declarations
body split_root: lines: 351 1706:2056 class HtmlDiff(object)
body split_class: lines: 21 1:21 class HtmlDiff(object)::Declarations
body split_class: lines: 17 22:38 class HtmlDiff(object)::__init__
body split_class: lines: 27 39:65 class HtmlDiff(object)::make_file
body split_class: lines: 23 66:88 class
HtmlDiff(object)::_tab_newline_replace
body split_class: lines: 55 89:143 class HtmlDiff(object)::_split_line
body split_class: lines: 28 144:171 class
HtmlDiff(object)::_line_wrapper
body split_class: lines: 21 172:192 class
HtmlDiff(object)::_collect_lines
body split_class: lines: 23 193:215 class HtmlDiff(object)::_format_line
body split_class: lines: 11 216:226 class HtmlDiff(object)::_make_prefix
body split_class: lines: 47 227:273 class
HtmlDiff(object)::_convert_flags
body split_class: lines: 77 274:350 class HtmlDiff(object)::make_table
body split_root: lines: 2 2057:2058 Declarations
body split_root: lines: 32 2059:2090 restore
body split_root: lines: 6 2091:2096 _test
This "picture" shows what is happening. Pay particular attention to the
ranges of line numbers.
The `class HtmlDiff` node contains 351 lines, which split_class then
"allocates" to child nodes. The picture shows that the child nodes "cover"
the original lines.
Edward
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