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- # templates.py
- import fileinput, re
- # Matches fields enclosed in square brackets:
- field_pat = re.compile(r'\[(.+?)\]')
- # We'll collect variables in this:
- scope = {}
- # This is used in re.sub:
- def replacement(match):
- code = match.group(1)
- try:
- # If the field can be evaluated, return it:
- return str(eval(code, scope))
- except SyntaxError:
- # Otherwise, execute the assignment in the same scope ...
- exec code in scope
- # ... and return an empty string:
- return ''
- # Get all the text as a single string:
- # (There are other ways of doing this; see Chapter 11)
- lines = []
- for line in fileinput.input():
- lines.append(line)
- text = ''.join(lines)
- # Substitute all the occurrences of the field pattern:
- print(field_pat.sub(replacement, text))
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