python 3 : replace text in a file

Question

I have a file city.py，I want to do two things below：

1.copy city.py to be newyork.py and losangeles.py.

2.there is a word city in city.py,I want to replace it with newyorkand losangeles.

I write a file copy_city.py to do this：

import shutil

def copy_city():
    cities = ['newyork', 'losangeles']
    for c in cities:
        city_file_name = c +'.py'
        shutil.copyfile('city.py',city_file_name)
        with open(city_file_name, "r+") as f:
            read_data = f.read()
            read_data.replace('city', c)



if __name__ == "__main__":
    copy_city()

question： The file city.py can be copied successfully,but the word city in file newyork.py and losangeles.py can not be replaced.why is it?

`File "c.py", line 8, in copy_city with open(city_file, "r+") as f: NameError: name 'city_file' is not defined` — tread, Aug 28 '17 at 18:11
`replace` does not modify the file in-place, it returns a new string with the replaces values — Wondercricket, Aug 28 '17 at 18:12
@surfer190 `city_file` should be `city_file_name`,I have update it. — zwl1619, Aug 28 '17 at 18:31
Possible duplicate of [How to modify a text file?](https://stackoverflow.com/questions/125703/how-to-modify-a-text-file) — Tadhg McDonald-Jensen, Aug 28 '17 at 18:35

score 0 · Answer 1 · answered Aug 28 '17 at 20:49

I used this answer about reading and writing contents to the same file

import shutil

def copy_city():
    cities = ['newyork', 'losangeles']
    for c in cities:
        city_file_name = c +'.py'
        line = ''
        shutil.copyfile('city.py',city_file_name)
        with open(city_file_name, "r") as f:
            read_data = f.read()
            line = read_data.replace('city', c)
            f.close()

        with open(city_file_name, "w") as f:
          f.write(line)
          f.close()

if __name__ == "__main__":
    copy_city()

python 3 : replace text in a file

1 Answers1