Snippets

SFTP a file

    import paramiko

    def fetch_remote_file(hostname, username, password, remote_file_path, local_file_path):
        with paramiko.Transport(hostname, 22) as transport:
            transport.connect(username, password)
            with paramiko.sftp_client.SFTPClient.from_transport(transport) as sftp:
                sftp.get(remote_file_path, local_file_path)

Memoize a function

from functools import wraps

def memoize(func):
    @wraps(func)
    def memoizer(*args, **kwargs):
        key = func.__name__ + str(<something dependent on the input params>)
        if cache_enabled:
            cached_value = cache.get(key, None)
            if cached_value is not None:
                return cached_value
        result = func(*args, **kwargs)
        cache.set(key, result)
        return result
    return memoizer

• Reference - Ned Batchelder

File

• list all entries in a directory - return [f.name for f in os.scandir(self.data_folder) if f.is_dir()]
• read contents of a file - contents = Path(file_path).read_text()

Misc

• Combine array of strings to single string ''.join(str_list)
• String interpolation "Input string goes here %s" % str_value
• To convert a list of strings in the correct order to a NamedTuple use MyNamedTuple._make(str_list)
• Sort list using sorted(my_list)
• Pretty print json using python3 -m json.tool

Map

• Map a function on a list list(map(func, orig_list))
• Can use a lambda if you want to modify the element list(map(lambda x: func(x.foo()), orig_list))
• Result can be passed to functions like list() or set()
• Equivalent to list comprehensions [func(x) for x in orig_list]

Reading from Excel File

• Use the xlrd library

  wb = xlrd.open_workbook(loc)  
  sheet = wb.sheet_by_name("My sheet")
  for row in sheet.get_rows()
    # Do something with row[col_number].value