I want to change a.txt to b.kml.

Use os.rename:

import os

os.rename('a.txt', 'b.kml')

File may be inside a directory, in that case specify the path:

import os
old_file = os.path.join("directory", "a.txt")
new_file = os.path.join("directory", "b.kml")
os.rename(old_file, new_file)

import shutil

shutil.move('a.txt', 'b.kml')

This will work to rename or move a file.

As of Python 3.4 one can use the pathlib module to solve this.

If you happen to be on an older version, you can use the backported version found here

Let’s assume you are not in the root path (just to add a bit of difficulty to it) you want to rename, and have to provide a full path, we can look at this:

some_path = 'a/b/c/the_file.extension'

So, you can take your path and create a Path object out of it:

from pathlib import Path
p = Path(some_path)

Just to provide some information around this object we have now, we can extract things out of it. For example, if for whatever reason we want to rename the file by modifying the filename from the_file to the_file_1, then we can get the filename part:

name_without_extension = p.stem

And still hold the extension in hand as well:

ext = p.suffix

We can perform our modification with a simple string manipulation:

Python 3.6 and greater make use of f-strings!

new_file_name = f"{name_without_extension}_1"

Otherwise:

new_file_name = "{}_{}".format(name_without_extension, 1)

And now we can perform our rename by calling the rename method on the path object we created and appending the ext to complete the proper rename structure we want:

p.rename(Path(p.parent, new_file_name + ext))

More shortly to showcase its simplicity:

Python 3.6+:

from pathlib import Path
p = Path(some_path)
p.rename(Path(p.parent, f"{p.stem}_1_{p.suffix}"))

Versions less than Python 3.6 use the string format method instead:

from pathlib import Path
p = Path(some_path)
p.rename(Path(p.parent, "{}_{}_{}".format(p.stem, 1, p.suffix))

os.rename(old, new)

This is found in the Python docs: http://docs.python.org/library/os.html

Use os.rename. But you have to pass full path of both files to the function. If I have a file a.txt on my desktop so I will do and also I have to give full of renamed file too.

 os.rename('C:\\Users\\Desktop\\a.txt', 'C:\\Users\\Desktop\\b.kml')

import os

# Set the path
path = 'a\\b\\c'  
# save current working directory
saved_cwd = os.getcwd()
# change your cwd to the directory which contains files
os.chdir(path)
os.rename('a.txt', 'b.klm')
# moving back to the directory you were in 
os.chdir(saved_cwd)

You can use os.system to invoke terminal to accomplish the task:

os.system('mv oldfile newfile')

import os
import re
from pathlib import Path

for f in os.listdir(training_data_dir2):
  for file in os.listdir( training_data_dir2 + '/' + f):
    oldfile= Path(training_data_dir2 + '/' + f + '/' + file)
    newfile = Path(training_data_dir2 + '/' + f + '/' + file[49:])
    p=oldfile
    p.rename(newfile)

import shutil
import os

files = os.listdir("./pics/") 

for key in range(0, len(files)):
   print files[key]
   shutil.move("./pics/" + files[key],"./pics/img" + str(key) + ".jpeg")

This should do it. python 3+