As one can find in python-pptx's documentation at https://python-pptx.readthedocs.io/en/latest/api/text.html
- a text frame is made up of paragraphs and
- a paragraph is made up of runs and specifies a font configuration that is used as the default for it's runs.
- runs specify part of the paragraph's text with a certain font configuration - possibly different from the default font configuration in the paragraph
All three have a field called text:
- The text frame's
text contains all the text from all it's paragraphs concatenated together with the appropriate line-feeds in between the paragraphs.
- The paragraphs's
text contains all the texts from all of it's runs concatenated to a long string with a vertical tab character (\v) put wherever there was a so-called soft-break in any of the run's text (a soft break is like a line-feed but without terminating the paragraph).
- The run's
text contains text that is to be rendered with a certain font configuration (font family, font size, italic/bold/underlined, color etc. pp). It is the lowest level of the font configuration for any text.
Now if you specify a line of text in a text-frame in a PowerPoint presentation, this text-frame will very likely only have one paragraph and that paragraph will have just one run.
Let's say that line says: Hi there! How are you? What is your name? and is all normal (neither italic nor bold) and in size 10.
Now if you go ahead in PowerPoint and make the questions How are you? What is your name? stand out by making them italic, you will end up with 2 runs in our paragraph:
Hello there! with the default font configuration from the paragraphHow are you? What is you name? with the font configuration specifying the additional italic attribute.
Now imagine, we want the How are you? stand out even more by making it bold and italic. We end up with 3 runs:
Hello there! with the default font configuration from the paragraph.How are you? with the font configuration specifying the BOLD and ITALIC attribute What is your name? with the font configuration specifying the ITALIC attribute.
One step further, making the are in How are you? bigger. We get 5 runs:
Hello there! with the default font configuration from the paragraph.How with the font configuration specifying the BOLD and ITALIC attributeare with the font configuration specifying the BOLD and ITALIC attribute and font size 16 you? with the font configuration specifying the BOLD and ITALIC attribute What is your name? with the font configuration specifying the ITALIC attribute.
So if you try to replace the How are you? with I'm fine! with the code from your question, you won't succeed, because the text How are you? is actually distributed across 3 runs.
You can go one level higher and look at the paragraph's text, that still says Hello there! How are you? What is your name? since it is the concatenation of all its run's texts.
But if you go ahead and do the replacement of the paragraph's text, it will erase all runs and create one new run with the text Hello there! I'm fine! What is your name? all the while deleting all the formatting that we put on the What is your name?.
Therefore, changing text in a paragraph without affecting formatting of the other text in the paragraph is pretty involved. And even if the text you are looking for has all the same formatting, that is no guarantee for it to be within one run. Because if you - in our example above - make the are smaller again, the 5 runs will very likely remain, the runs 2 to 4 just having the same font configuration now.
Here is the code to produce a test presentation with a text box containing the exact paragraph runs as given in my example above:
from pptx import Presentation
from pptx.chart.data import CategoryChartData
from pptx.enum.chart import XL_CHART_TYPE,XL_LABEL_POSITION
from pptx.util import Inches, Pt
from pptx.dml.color import RGBColor
from pptx.enum.dml import MSO_THEME_COLOR
# create presentation with 1 slide ------
prs = Presentation()
slide = prs.slides.add_slide(prs.slide_layouts[5])
textbox_shape = slide.shapes.add_textbox(Pt(200),Pt(200),Pt(30),Pt(240))
text_frame = textbox_shape.text_frame
p = text_frame.paragraphs[0]
font = p.font
font.name = 'Arial'
font.size = Pt(10)
font.bold = False
font.italic = False
font.color.rgb = RGBColor(0,0,0)
run = p.add_run()
run.text = 'Hello there! '
run = p.add_run()
run.text = 'How '
font = run.font
font.italic = True
font.bold = True
run = p.add_run()
run.text = 'are'
font = run.font
font.italic = True
font.bold = True
font.size = Pt(16)
run = p.add_run()
run.text = ' you?'
font = run.font
font.italic = True
font.bold = True
run = p.add_run()
run.text = ' What is your name?'
run.font.italic = True
prs.save('text-01.pptx')
And this is what it looks like, if you open it in PowerPoint:
Now if you use this code on it:
from pptx import Presentation
from pptx.chart.data import CategoryChartData
from pptx.shapes.graphfrm import GraphicFrame
from pptx.enum.chart import XL_CHART_TYPE
from pptx.util import Inches
def replace_text(replacements, shapes):
for shape in shapes:
if shape.has_text_frame:
text_frame = shape.text_frame
for (match, replacement) in replacements.items():
if text_frame.text.find(match)>=0:
for paragraph in text_frame.paragraphs:
pos = paragraph.text.find(match)
while pos>=0:
replace_runs_text(paragraph.runs, pos, len(match), replacement)
pos = paragraph.text.find(match)
def replace_runs_text(runs, pos, match_len, replacement):
cnt = len(runs)
i = 0
while i<cnt:
olen = len(runs[i].text)
if pos<olen:
# we found the run, where the match starts!
to_replace = replacement
repl_len = len(to_replace)
while i<cnt:
run = runs[i]
otext = run.text
olen = len(otext)
if pos+match_len < olen:
# our match ends before the end of the text of this run therefore
# we put the rest of our replacement string here and we are done!
run.text = otext[0:pos]+to_replace+otext[pos+match_len:]
return
if pos+match_len == olen:
# our match ends together with the text of this run therefore
# we put the rest of our replacement string here and we are done!
run.text = otext[0:pos]+to_replace
return
# we still haven't found all of our original match string
# so we process what we have here and go on to the next run
part_match_len = olen-pos
ntext = otext[0:pos]
if repl_len <= part_match_len:
# we now found at least as many characters for our match string
# as we have replacement characters for it. Thus we use up the
# the rest of our replacement string here and will replace the
# remainder of the match with an empty string (which happens
# to happen in this exact same spot for the next run ;-))
ntext += to_replace
repl_len = 0
to_replace = ''
else:
# we have got some more match characters but still more
# replacement characters than match characters found
ntext += to_replace[0:part_match_len]
to_replace = to_replace[part_match_len:]
repl_len -= part_match_len
run.text = ntext # save the new text to the run
match_len -= part_match_len # this is what is left to match
pos = 0 # in the next run, we start at pos 0 with our match
i += 1 # and off to the next run
else:
pos -= olen # the relative position of our match in the next run's text
i += 1 # and off to the next run
# create presentation with 1 slide ------
prs = Presentation('text-01.pptx')
# what is to be replaced
replacements = { 'How are you?': "I'm fine!" }
# loop through all slides and replace text in all their shapes
for slide in prs.slides:
replace_text(replacements, slide.shapes)
# save changed presentation
prs.save('text-02.pptx')
the resulting presentation looks like this:
As you can see, it mapped the replacement string exactly onto the existing font-configurations, thus if your match and it's replacement have the same length, the replacement string will retain the exact format of the match.
But - as an important side-note - if the text-frame has auto-size or fit-frame switched on, even all that work won't save you from screwing up the formatting, if the text after the replacement needs more or less space!
