Add untokenize() function to allow full round-trip tokenization.
Should significantly enhance the utility of the module by supporting
the creation of tools that modify the token stream and writeback the
modified result.
diff --git a/Lib/tokenize.py b/Lib/tokenize.py
index 9087e84..b29da6b 100644
--- a/Lib/tokenize.py
+++ b/Lib/tokenize.py
@@ -31,7 +31,7 @@
import token
__all__ = [x for x in dir(token) if x[0] != '_'] + ["COMMENT", "tokenize",
- "generate_tokens", "NL"]
+ "generate_tokens", "NL", "untokenize"]
del x
del token
@@ -159,12 +159,55 @@
for token_info in generate_tokens(readline):
tokeneater(*token_info)
+
+def untokenize(iterable):
+ """Transform tokens back into Python source code.
+
+ Each element returned by the iterable must be a token sequence
+ with at least two elements, a token number and token value.
+
+ Round-trip invariant:
+ # Output text will tokenize the back to the input
+ t1 = [tok[:2] for tok in generate_tokens(f.readline)]
+ newcode = untokenize(t1)
+ readline = iter(newcode.splitlines(1)).next
+ t2 = [tok[:2] for tokin generate_tokens(readline)]
+ assert t1 == t2
+ """
+
+ startline = False
+ indents = []
+ toks = []
+ toks_append = toks.append
+ for tok in iterable:
+ toknum, tokval = tok[:2]
+
+ if toknum == NAME:
+ tokval += ' '
+
+ if toknum == INDENT:
+ indents.append(tokval)
+ continue
+ elif toknum == DEDENT:
+ indents.pop()
+ continue
+ elif toknum in (NEWLINE, COMMENT, NL):
+ startline = True
+ elif startline and indents:
+ toks_append(indents[-1])
+ startline = False
+ toks_append(tokval)
+ return ''.join(toks)
+
+
def generate_tokens(readline):
"""
The generate_tokens() generator requires one argment, readline, which
must be a callable object which provides the same interface as the
readline() method of built-in file objects. Each call to the function
- should return one line of input as a string.
+ should return one line of input as a string. Alternately, readline
+ can be a callable function terminating with StopIteration:
+ readline = open(myfile).next # Example of alternate readline
The generator produces 5-tuples with these members: the token type; the
token string; a 2-tuple (srow, scol) of ints specifying the row and
@@ -180,7 +223,10 @@
indents = [0]
while 1: # loop over lines in stream
- line = readline()
+ try:
+ line = readline()
+ except StopIteration:
+ line = ''
lnum = lnum + 1
pos, max = 0, len(line)