Close #13857: Added textwrap.indent() function (initial patch by Ezra

Berch)

Lib/textwrap.py

@@ -7,7 +7,7 @@
 
 import re
 
-__all__ = ['TextWrapper', 'wrap', 'fill', 'dedent']
+__all__ = ['TextWrapper', 'wrap', 'fill', 'dedent', 'indent']
 
 # Hardcode the recognized whitespace characters to the US-ASCII
 # whitespace characters.  The main reason for doing this is that in
@@ -386,6 +386,25 @@ def dedent(text):
         text = re.sub(r'(?m)^' + margin, '', text)
     return text
 
+
+def indent(text, prefix, predicate=None):
+    """Adds 'prefix' to the beginning of selected lines in 'text'.
+
+    If 'predicate' is provided, 'prefix' will only be added to the lines
+    where 'predicate(line)' is True. If 'predicate' is not provided,
+    it will default to adding 'prefix' to all non-empty lines that do not
+    consist solely of whitespace characters.
+    """
+    if predicate is None:
+        def predicate(line):
+            return line.strip()
+
+    def prefixed_lines():
+        for line in text.splitlines(True):
+            yield (prefix + line if predicate(line) else line)
+    return ''.join(prefixed_lines())
+
+
 if __name__ == "__main__":
     #print dedent("\tfoo\n\tbar")
     #print dedent("  \thello there\n  \t  how are you?")