Updated to support multiple replaces of the same KEY in a PARAGRAPH

python-docx-replace-text-and-retain-style.py

def docx_replace(doc, data):
	paragraphs = list(doc.paragraphs)
	for t in doc.tables:
		for row in t.rows:
			for cell in row.cells:
				for paragraph in cell.paragraphs:
					paragraphs.append(paragraph)
	for p in paragraphs:
		for key, val in data.items():
			key_name = '${{{}}}'.format(key) # use placeholders in the form ${PlaceholderName}
			if key_name in p.text:
				inline = p.runs
				replace_inline(key_name, val, inline)	
	
	
	
	def replace_inline(key_name, val, inline):
		# Replace strings and retain the same style.
		# The text to be replaced can be split over several runs so
		# search through, identify which runs need to have text replaced
		# then replace the text in those identified
		started = False
		key_index = 0
		# found_runs is a list of (inline index, index of match, length of match)
		found_runs = list()
		found_all = False
		replace_done = False
		for i in range(len(inline)):

			# case 1: found in single run so short circuit the replace
			if key_name in inline[i].text and not started:
				found_runs.append((i, inline[i].text.find(key_name), len(key_name)))
				text = inline[i].text.replace(key_name, str(val))
				inline[i].text = text
				replace_done = True
				found_all = True
				break

			if key_name[key_index] not in inline[i].text and not started:
				# keep looking ...
				continue

			# case 2: search for partial text, find first run
			if key_name[key_index] in inline[i].text and inline[i].text[-1] in key_name and not started:
				# check sequence
				start_index = inline[i].text.find(key_name[key_index])
				check_length = len(inline[i].text)
				for text_index in range(start_index, check_length):
					if inline[i].text[text_index] != key_name[key_index]:
						# no match so must be false positive
						break
				if key_index == 0:
					started = True
				chars_found = check_length - start_index
				key_index += chars_found
				found_runs.append((i, start_index, chars_found))
				if key_index != len(key_name):
					continue
				else:
					# found all chars in key_name
					found_all = True
					break

			# case 2: search for partial text, find subsequent run
			if key_name[key_index] in inline[i].text and started and not found_all:
				# check sequence
				chars_found = 0
				check_length = min(len(inline[i].text), len(key_name[key_index]) - key_index)
				for text_index in range(0, check_length):
					if inline[i].text[text_index] == key_name[key_index]:
						key_index += 1
						chars_found += 1
					else:
						break
				# no match so must be end
				found_runs.append((i, 0, chars_found))
				if key_index == len(key_name):
					found_all = True
					break

		if found_all and not replace_done:
			for i, item in enumerate(found_runs):
				index, start, length = [t for t in item]
				if i == 0:
					text = inline[index].text.replace(inline[index].text[start:start + length], str(val))
					inline[index].text = text
				else:
					text = inline[index].text.replace(inline[index].text[start:start + length], '')
					inline[index].text = text
			if key_name in p.text:
				replace_inline(key_name, val, inline)	
				
# usage
doc = docx.Document('path/to/template.docx')
docx_replace(doc, dict(ItemOne='replacement text', ItemTwo="Some replacement text\nand some more")
doc.save('path/to/destination.docx')