change string in MS word

[Mr_Blue]

hello,
i would like to change a word in a word document.

from docx import Document
document = Document('/path/word_template.docx')
doc = docx.Document()

VAR1 = input('FIRST_NAME: ')
VAR2 = input('LAST_NAME: ')

for paragraph in document.paragraphs:
    if 'FIRST_NAME' in paragraph.text:
        print paragraph.text
        paragraph.text = VAR1
    elif 'LAST_NAME' in paragraph.text
        print paragraph.text
        paragraph.text = VAR1

doc.save('/path/word_template.docx')

Error:
Traceback (most recent call last):
  File "test1.py", line 1, in <module>
    from docx import Document
ModuleNotFoundError: No module named 'docx'

how odd.

OS: linux
python 2 et 3 used to no avail