How do I copy an entire directory of files into an existing directory using Python?

Beyond the basic: Exceptional conditions and Python versions

Workaround for Python < 3.8

OSError likes to crash the party if your Python version < 3.8. The copy_tree function from the distutils.dir_util module can help you handle that:

from distutils.dir_util import copy_tree

copy_tree('/source/dir', '/target/existing/dir')  # No gate crashing OSError today!
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Playing nice with symlinks and permissions

Look out for symlinks and file permissions while copying. You don't want to leave anything behind:

def custom_copy(src, dst):
    os.makedirs(dst, exist_ok=True)
    for item in os.listdir(src):
        s = os.path.join(src, item)
        d = os.path.join(dst, item)
        if os.path.islink(s):
            linkto = os.readlink(s)
            os.symlink(linkto, d)  # Creating a new link to the past
            os.lchmod(d, os.lstat(s).st_mode)  # I find your lack of permissions disturbing
        elif os.path.isdir(s):
            custom_copy(s, d)  # What's recursion's concept? See line 2
        else:
            shutil.copy2(s, d)  # Copy2 strikes back
custom_copy('/source/dir', '/target/existing/dir')
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Catch errors while they last

Preferred way to handle errors like a pro is to catch the returned shutil.Error:

try:
    custom_copy('/source/dir', '/target/existing/dir')
except shutil.Error as e:
    print(f'Error: {e}')  # Detective Python will crack the Error Case
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Various scenarios when copying directories

Selective updates: only fresh gets served

Updating files selectively, like careful chefs adding seasoning to a dish:

import os, shutil, filecmp

def selective_copy(src, dst):
    # If directory doesn't exist or file is fresher than its copy, copy it. `shallow=False` for the chef's touch
    if not os.path.exists(dst) or not filecmp.cmp(src, dst, shallow=False):
        shutil.copy2(src, dst)
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Use this function instead of shutil.copy2 in recursive_copy.

Strictly subdirectories: Files need not apply

If you don't want to copy top-level files but only subdirectories, filter them out:

from pathlib import Path

def dirs_only_copy(src, dst):
    for item in Path(src).iterdir():
        if item.is_dir():
            recursive_copy(str(item), os.path.join(dst, item.name))
dirs_only_copy('/source/dir', '/target/existing/dir')  # It's the Subdirectories Only Club
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Copying and applying file status metadata

For those wanting an exact replica, use shutil.copystat after copying to apply metadata:

import shutil

# After executing recursive_copy
shutil.copystat('/source/dir', '/target/existing/dir')  # It's Twilight Zone time: Mirror Image 
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