Python Script: Find Duplicate Files (Source code download)

Have you ever wondered how to check duplicate files in Python? If so, this blog post is for you! Checking for duplicate files can be a pain, but luckily there is a Python module for that. In this blog post, we will show you how to use the Python module “hashlib” to check for duplicate files. We will also provide a demo script that you can use to check for duplicates on your own computer.

Why Check for Duplicate Files?

There are many reasons why you might want to check for duplicate files. Maybe you are trying to free up some disk space, or maybe you are trying to find out if two files are the same. Regardless of your reason, checking for duplicates can be important.

What is Hashlib?

Hashlib is a Python module that allows you to generate hashes for strings. A hash is a way of encoding data so that it can be compared more easily. For example, the MD5 hash of the string “hello world” is “d3b07384d113edec49eaa6238ad5ff00”. Given two strings, you can use a hash function to generate a hash for each string. If the two hashes are the same, then you know that the two strings are also the same. This is useful for comparing files because it means that you can compare two files without having to read through them both completely.

How to Use Hashlib

Using hashlib is simple. First, import the module using “import hashlib”. Then, use the “hashlib.md5()” function to create a new MD5 hash object. Finally, call the “update()” function on your hash object with the string or file that you want to generate a hash for. This will return a hash value as a hexadecimal string.

Full Python Script

""" Script to find duplicate files in a given path """ import os import hashlib from sys import argv # will store file realted info # structure: keys => file size # values = a dict(), structure: keys => is_duplicate, filepath, sha1, sha256 files = {} # will store duplicate files # structure: keys => filepath of parent file in group of duplicates # values = a list of filepath of duplicates dups = {} stats = { "total_files": 0, "current_file": 0, "duplicates": 0, "size": 0 } def progress(): print( """\r[{0}/{1}] files checked || \b[{2}/{3}] duplicates found.""". format( stats["current_file"], stats["total_files"], stats["duplicates"], stats["current_file"] ), end="") def load(path): path = os.walk(path) for dirpath, dirnames, filenames in path: for filename in filenames: filepath = os.path.join(dirpath, filename) # skips symbolic link if not os.path.islink(filepath): key = os.path.getsize(filepath) if key not in files: files[key] = [] stats["total_files"] += 1 print(f"\rFiles Traversed: {stats['total_files']}", end="") files[key].append({ "is_duplicate": False, "filepath": filepath, }) def add_sha1(file_info): BUF_SIZE = 1024 sha1 = hashlib.sha1() with open(file_info["filepath"], 'rb') as file: data = sha1.update(data) file_info["sha1"] = sha1.hexdigest() def is_equal_sha1(file1_info, file2_info): add_sha1(file1_info) add_sha1(file2_info) return file1_info["sha1"] == file2_info["sha1"] def add_sha256(file_info): BUF_SIZE = 65536 sha256 = hashlib.sha256() with open(file_info["filepath"], 'rb') as file: while True: data = if not data: break sha256.update(data) file_info["sha256"] = sha256.hexdigest() def is_equal_sha256(file1_info, file2_info): if "sha256" not in file1_info: add_sha256(file1_info) if "sha256" not in file2_info: add_sha256(file2_info) return file1_info["sha256"] == file2_info["sha256"] def find(): for key in files: # pick file from a group for idx, file1_info in enumerate(files[key]): # skip if already in list of duplicates if file1_info["is_duplicate"]: continue # compare picked file with file to the right for ptr in range(idx + 1, len(files[key])): file2_info = files[key][ptr] # skip if already in list of duplicates if file2_info["is_duplicate"]: continue if is_equal_sha1(file1_info, file2_info): if is_equal_sha256(file1_info, file2_info): file2_info["is_duplicate"] = True stats["duplicates"] += 1 stats["size"] += key if file1_info["filepath"] not in dups: dups[file1_info["filepath"]] = [] dups[file1_info["filepath"]].append( file2_info["filepath"]) # update progress stats["current_file"] += len(files[key]) progress() def store(): with open("duplicates.txt", "w") as file: for key in dups: file.write(f"Duplicate of {key} is at:\n") for entry in dups[key]: file.write(entry + "\n") file.write("\n\n") def print_stats(): print("\n\nTotal no of duplicates:", stats["duplicates"]) KB = 1024 MB = 1024 * 1024 GB = 1024 * 1024 * 1024 dupsSize = stats["size"] if dupsSize >= GB: print("Total space taken by duplicates: %.02lf GB" % (dupsSize / GB)) elif dupsSize >= MB: print("Total space taken by duplicates: %.02lf MB" % (dupsSize / MB)) elif dupsSize >= KB: print("Total space taken by duplicates: %.02lf KB" % (dupsSize / KB)) else: print(f"Total space taken by duplicates: {dupsSize} Bytes") def main(): # Validate command line args if not len(argv) > 1: print("Usage: python <path>") return start_path = argv[1] # traverse file tree and group files on the basis of there size load(start_path) # find duplicates find() # writes duplicates in a file store() print_stats() if __name__ == "__main__": main()
Code language: Python (python)


python <path_to_directory>
Code language: HTML, XML (xml)

A file with the name duplicates.txt will be created containing list of duplicate files.


Checking for duplicate files can be important for many reasons. Luckily, there is a Python module that makes it easy to do – hashlib! In this blog post, we showed you how to use hashlib to check for duplicates. We also provided a demo script that you can use on your own computer. Thanks for reading!

Andy Avery

I really enjoy helping people with their tech problems to make life easier, ​and that’s what I’ve been doing professionally for the past decade.

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