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"""Analysis of text input into executable blocks.
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This is a simple example of how an interactive terminal-based client can use
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this tool::
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bb = BlockBreaker()
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while not bb.interactive_block_ready():
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bb.push(raw_input('>>> '))
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print 'Input source was:\n', bb.source,
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"""
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#-----------------------------------------------------------------------------
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# Copyright (C) 2010 The IPython Development Team
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#
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# Distributed under the terms of the BSD License. The full license is in
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# the file COPYING, distributed as part of this software.
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#-----------------------------------------------------------------------------
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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# stdlib
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import codeop
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import re
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import sys
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#-----------------------------------------------------------------------------
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# Utilities
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#-----------------------------------------------------------------------------
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# FIXME: move these utilities to the general ward...
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# compiled regexps for autoindent management
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dedent_re = re.compile(r'^\s+raise|^\s+return|^\s+pass')
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ini_spaces_re = re.compile(r'^([ \t\r\f\v]+)')
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def num_ini_spaces(s):
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"""Return the number of initial spaces in a string.
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Note that tabs are counted as a single space. For now, we do *not* support
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mixing of tabs and spaces in the user's input.
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Parameters
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----------
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s : string
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"""
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ini_spaces = ini_spaces_re.match(s)
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if ini_spaces:
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return ini_spaces.end()
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else:
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return 0
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def remove_comments(src):
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"""Remove all comments from input source.
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Note: comments are NOT recognized inside of strings!
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Parameters
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----------
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src : string
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A single or multiline input string.
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Returns
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-------
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String with all Python comments removed.
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"""
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return re.sub('#.*', '', src)
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def get_input_encoding():
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"""Return the default standard input encoding."""
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return getattr(sys.stdin, 'encoding', 'ascii')
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#-----------------------------------------------------------------------------
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# Classes and functions
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#-----------------------------------------------------------------------------
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class BlockBreaker(object):
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# Command compiler
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compile = None
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# Number of spaces of indentation
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indent_spaces = 0
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# Mark when input has changed indentation all the way back to flush-left
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full_dedent = False
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# String, indicating the default input encoding
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encoding = ''
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# String where the current full source input is stored, properly encoded
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source = ''
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# Code object corresponding to the current source
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code = None
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# Boolean indicating whether the current block is complete
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is_complete = None
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# Input mode
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input_mode = 'append'
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# Private attributes
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# List
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_buffer = None
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def __init__(self, input_mode=None):
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"""Create a new BlockBreaker instance.
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Parameters
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----------
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input_mode : str
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One of 'append', 'replace', default is 'append'. This controls how
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new inputs are used: in 'append' mode, they are appended to the
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existing buffer and the whole buffer is compiled; in 'replace' mode,
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each new input completely replaces all prior inputs. Replace mode is
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thus equivalent to prepending a full reset() to every push() call.
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In practice, line-oriented clients likely want to use 'append' mode
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while block-oriented ones will want to use 'replace'.
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"""
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self._buffer = []
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self.compile = codeop.CommandCompiler()
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self.encoding = get_input_encoding()
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self.input_mode = BlockBreaker.input_mode if input_mode is None \
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else input_mode
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def reset(self):
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"""Reset the input buffer and associated state."""
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self.indent_spaces = 0
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self._buffer[:] = []
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self.source = ''
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self.code = None
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self.is_complete = False
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self.full_dedent = False
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def source_reset(self):
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"""Return the input source and perform a full reset.
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"""
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out = self.source
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self.reset()
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return out
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def push(self, lines):
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"""Push one ore more lines of input.
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This stores the given lines and returns a status code indicating
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whether the code forms a complete Python block or not.
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Any exceptions generated in compilation are allowed to propagate.
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Parameters
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----------
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lines : string
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One or more lines of Python input.
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Returns
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-------
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is_complete : boolean
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True if the current input source (the result of the current input
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plus prior inputs) forms a complete Python execution block. Note that
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this value is also stored as an attribute so it can be queried at any
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time.
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"""
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if self.input_mode == 'replace':
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self.reset()
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# If the source code has leading blanks, add 'if 1:\n' to it
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# this allows execution of indented pasted code. It is tempting
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# to add '\n' at the end of source to run commands like ' a=1'
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# directly, but this fails for more complicated scenarios
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if not self._buffer and lines[:1] in [' ', '\t']:
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lines = 'if 1:\n%s' % lines
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self._store(lines)
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source = self.source
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# Before calling compile(), reset the code object to None so that if an
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# exception is raised in compilation, we don't mislead by having
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# inconsistent code/source attributes.
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self.code, self.is_complete = None, None
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self._update_indent(lines)
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try:
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self.code = self.compile(source)
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# Invalid syntax can produce any of a number of different errors from
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# inside the compiler, so we have to catch them all. Syntax errors
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# immediately produce a 'ready' block, so the invalid Python can be
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# sent to the kernel for evaluation with possible ipython
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# special-syntax conversion.
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except (SyntaxError, OverflowError, ValueError, TypeError,
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MemoryError):
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self.is_complete = True
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else:
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# Compilation didn't produce any exceptions (though it may not have
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# given a complete code object)
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self.is_complete = self.code is not None
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return self.is_complete
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def interactive_block_ready(self):
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"""Return whether a block of interactive input is ready for execution.
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This method is meant to be used by line-oriented frontends, who need to
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guess whether a block is complete or not based solely on prior and
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current input lines. The BlockBreaker considers it has a complete
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interactive block when *all* of the following are true:
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1. The input compiles to a complete statement.
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2. The indentation level is flush-left (because if we are indented,
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like inside a function definition or for loop, we need to keep
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reading new input).
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3. There is one extra line consisting only of whitespace.
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Because of condition #3, this method should be used only by
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*line-oriented* frontends, since it means that intermediate blank lines
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are not allowed in function definitions (or any other indented block).
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Block-oriented frontends that have a separate keyboard event to
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indicate execution should use the :meth:`split_blocks` method instead.
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"""
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#print 'complete?', self.source # dbg
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|
#if self.full_dedent:
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# True
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if not self.is_complete:
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return False
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if self.indent_spaces==0:
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return True
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last_line = self.source.splitlines()[-1]
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if not last_line or last_line.isspace():
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return True
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else:
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return False
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def split_blocks(self, lines):
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|
"""Split a multiline string into multiple input blocks.
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|
Note: this method starts by performing a full reset().
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Parameters
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----------
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|
lines : str
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|
A possibly multiline string.
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Returns
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-------
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blocks : list
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A list of strings, each possibly multiline. Each string corresponds
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|
to a single block that can be compiled in 'single' mode (unless it
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|
has a syntax error)."""
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|
|
# This code is fairly delicate. If you make any changes here, make
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|
# absolutely sure that you do run the full test suite and ALL tests
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|
# pass.
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|
self.reset()
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|
blocks = []
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|
# Reversed copy so we can use pop() efficiently and consume the input
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|
|
# as a stack
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|
|
lines = lines.splitlines()[::-1]
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|
|
# Outer loop over all input
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|
|
while lines:
|
|
|
# Inner loop to build each block
|
|
|
while True:
|
|
|
# Safety exit from inner loop
|
|
|
if not lines:
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|
break
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|
|
# Grab next line but don't push it yet
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|
|
next_line = lines.pop()
|
|
|
# Blank/empty lines are pushed as-is
|
|
|
if not next_line or next_line.isspace():
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|
self.push(next_line)
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|
continue
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|
|
# Check indentation changes caused by the *next* line
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|
|
indent_spaces, full_dedent = self._find_indent(next_line)
|
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|
|
|
# If the next line causes a dedent, it can be for two differnt
|
|
|
# reasons: either an explicit de-dent by the user or a
|
|
|
# return/raise/pass statement. These MUST be handled
|
|
|
# separately:
|
|
|
#
|
|
|
# 1. the first case is only detected when the actual explicit
|
|
|
# dedent happens, and that would be the *first* line of a *new*
|
|
|
# block. Thus, we must put the line back into the input buffer
|
|
|
# so that it starts a new block on the next pass.
|
|
|
#
|
|
|
# 2. the second case is detected in the line before the actual
|
|
|
# dedent happens, so , we consume the line and we can break out
|
|
|
# to start a new block.
|
|
|
|
|
|
# Case 1, explicit dedent causes a break
|
|
|
if full_dedent and not next_line.startswith(' '):
|
|
|
lines.append(next_line)
|
|
|
break
|
|
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|
|
|
# Otherwise any line is pushed
|
|
|
self.push(next_line)
|
|
|
|
|
|
# Case 2, full dedent with full block ready:
|
|
|
if full_dedent or \
|
|
|
self.indent_spaces==0 and self.interactive_block_ready():
|
|
|
break
|
|
|
# Form the new block with the current source input
|
|
|
blocks.append(self.source_reset())
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|
|
|
|
|
return blocks
|
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|
|
|
|
#------------------------------------------------------------------------
|
|
|
# Private interface
|
|
|
#------------------------------------------------------------------------
|
|
|
|
|
|
def _find_indent(self, line):
|
|
|
"""Compute the new indentation level for a single line.
|
|
|
|
|
|
Parameters
|
|
|
----------
|
|
|
line : str
|
|
|
A single new line of non-whitespace, non-comment Python input.
|
|
|
|
|
|
Returns
|
|
|
-------
|
|
|
indent_spaces : int
|
|
|
New value for the indent level (it may be equal to self.indent_spaces
|
|
|
if indentation doesn't change.
|
|
|
|
|
|
full_dedent : boolean
|
|
|
Whether the new line causes a full flush-left dedent.
|
|
|
"""
|
|
|
indent_spaces = self.indent_spaces
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|
|
full_dedent = self.full_dedent
|
|
|
|
|
|
inisp = num_ini_spaces(line)
|
|
|
if inisp < indent_spaces:
|
|
|
indent_spaces = inisp
|
|
|
if indent_spaces <= 0:
|
|
|
#print 'Full dedent in text',self.source # dbg
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|
|
full_dedent = True
|
|
|
|
|
|
if line[-1] == ':':
|
|
|
indent_spaces += 4
|
|
|
elif dedent_re.match(line):
|
|
|
indent_spaces -= 4
|
|
|
if indent_spaces <= 0:
|
|
|
full_dedent = True
|
|
|
|
|
|
# Safety
|
|
|
if indent_spaces < 0:
|
|
|
indent_spaces = 0
|
|
|
#print 'safety' # dbg
|
|
|
|
|
|
return indent_spaces, full_dedent
|
|
|
|
|
|
def _update_indent(self, lines):
|
|
|
for line in remove_comments(lines).splitlines():
|
|
|
if line and not line.isspace():
|
|
|
self.indent_spaces, self.full_dedent = self._find_indent(line)
|
|
|
|
|
|
def _store(self, lines):
|
|
|
"""Store one or more lines of input.
|
|
|
|
|
|
If input lines are not newline-terminated, a newline is automatically
|
|
|
appended."""
|
|
|
|
|
|
if lines.endswith('\n'):
|
|
|
self._buffer.append(lines)
|
|
|
else:
|
|
|
self._buffer.append(lines+'\n')
|
|
|
self._set_source()
|
|
|
|
|
|
def _set_source(self):
|
|
|
self.source = ''.join(self._buffer).encode(self.encoding)
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|
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|
|
|
|
