def ecdsa_sign(private_key, data, hash_algorithm):
if not hasattr(private_key, '<STR_LIT>') or not isinstance(private_key.asn1, keys.PrivateKeyInfo):<EOL><INDENT>raise TypeError(pretty_message(<EOL>'''<STR_LIT>''',<EOL>type_name(private_key)<EOL>))<EOL><DEDENT>curve_name = private_key.curve<EOL>if curve_name not in set(['<STR_LIT>', '<STR_LIT>', '<STR_LIT>']):<EOL><INDENT>raise ValueError(pretty_message(<EOL>'''<STR_LIT>'''<EOL>))<EOL><DEDENT>if not isinstance(data, byte_cls):<EOL><INDENT>raise TypeError(pretty_message(<EOL>'''<STR_LIT>''',<EOL>type_name(data)<EOL>))<EOL><DEDENT>if hash_algorithm not in set(['<STR_LIT>', '<STR_LIT>', '<STR_LIT>', '<STR_LIT>', '<STR_LIT>']):<EOL><INDENT>raise ValueError(pretty_message(<EOL>'''<STR_LIT>''',<EOL>repr(hash_algorithm)<EOL>))<EOL><DEDENT>hash_func = getattr(hashlib, hash_algorithm)<EOL>ec_private_key = private_key.asn1['<STR_LIT>'].parsed<EOL>private_key_bytes = ec_private_key['<STR_LIT>'].contents<EOL>private_key_int = ec_private_key['<STR_LIT>'].native<EOL>curve_num_bytes = CURVE_BYTES[curve_name]<EOL>curve_base_point = {<EOL>'<STR_LIT>': SECP256R1_BASE_POINT,<EOL>'<STR_LIT>': SECP384R1_BASE_POINT,<EOL>'<STR_LIT>': SECP521R1_BASE_POINT,<EOL>}[curve_name]<EOL>n = curve_base_point.order<EOL>digest = hash_func(data).digest()<EOL>hash_length = len(digest)<EOL>h = int_from_bytes(digest, signed=False) % n<EOL>V = b'<STR_LIT>' * hash_length<EOL>K = b'<STR_LIT:\x00>' * hash_length<EOL>K = hmac.new(K, V + b'<STR_LIT:\x00>' + private_key_bytes + digest, hash_func).digest()<EOL>V = hmac.new(K, V, hash_func).digest()<EOL>K = hmac.new(K, V + b'<STR_LIT>' + private_key_bytes + digest, hash_func).digest()<EOL>V = hmac.new(K, V, hash_func).digest()<EOL>r = <NUM_LIT:0><EOL>s = <NUM_LIT:0><EOL>while True:<EOL><INDENT>T = b'<STR_LIT>'<EOL>while len(T) < curve_num_bytes:<EOL><INDENT>V = hmac.new(K, V, hash_func).digest()<EOL>T += V<EOL><DEDENT>k = int_from_bytes(T[<NUM_LIT:0>:curve_num_bytes], signed=False)<EOL>if k == <NUM_LIT:0> or k >= n:<EOL><INDENT>continue<EOL><DEDENT>r = (curve_base_point * k).x % n<EOL>if r == <NUM_LIT:0>:<EOL><INDENT>continue<EOL><DEDENT>s = (inverse_mod(k, n) * (h + (private_key_int * r) % n)) % n<EOL>if s == <NUM_LIT:0>:<EOL><INDENT>continue<EOL><DEDENT>break<EOL><DEDENT>return DSASignature({'<STR_LIT:r>': r, '<STR_LIT:s>': s}).dump()<EOL>
Generates an ECDSA signature in pure Python (thus slow)

:param private_key:
    The PrivateKey to generate the signature with

:param data:
    A byte string of the data the signature is for

:param hash_algorithm:
    A unicode string of "sha1", "sha256", "sha384" or "sha512"

:raises:
    ValueError - when any of the parameters contain an invalid value
    TypeError - when any of the parameters are of the wrong type
    OSError - when an error is returned by the OS crypto library

:return:
    A byte string of the signature