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# -*- coding: utf-8 -*-


This module provides utility functions that are used within Requests
that are also useful for external consumption.

import cgi
import codecs
import collections
import contextlib
import io
import os
import platform
import re
import socket
import struct
import warnings

from .__version__ import __version__
from . import certs
# to_native_string is unused here, but imported here for backwards compatibility
from ._internal_utils import to_native_string
from .compat import parse_http_list as _parse_list_header
from .compat import (
quote, urlparse, bytes, str, OrderedDict, unquote, getproxies,
proxy_bypass, urlunparse, basestring, integer_types, is_py3,
proxy_bypass_environment, getproxies_environment)
from .cookies import cookiejar_from_dict
from .structures import CaseInsensitiveDict
from .exceptions import (
InvalidURL, InvalidHeader, FileModeWarning, UnrewindableBodyError)

NETRC_FILES = ('.netrc', '_netrc')

DEFAULT_CA_BUNDLE_PATH = certs.where()

if platform.system() == 'Windows':
# provide a proxy_bypass version on Windows without DNS lookups

def proxy_bypass_registry(host):
if is_py3:
import winreg
import _winreg as winreg
internetSettings = winreg.OpenKey(winreg.HKEY_CURRENT_USER,
r'Software\Microsoft\Windows\CurrentVersion\Internet Settings')
proxyEnable = winreg.QueryValueEx(internetSettings,
proxyOverride = winreg.QueryValueEx(internetSettings,
except OSError:
return False
if not proxyEnable or not proxyOverride:
return False

# make a check value list from the registry entry: replace the
# '' string by the localhost entry and the corresponding
# canonical entry.
proxyOverride = proxyOverride.split(';')
# now check if we match one of the registry values.
for test in proxyOverride:
if test == '':
if '.' not in host:
return True
test = test.replace(".", r"\.") # mask dots
test = test.replace("*", r".*") # change glob sequence
test = test.replace("?", r".") # change glob char
if re.match(test, host, re.I):
return True
return False

def proxy_bypass(host): # noqa
"""Return True, if the host should be bypassed.

Checks proxy settings gathered from the environment, if specified,
or the registry.
if getproxies_environment():
return proxy_bypass_environment(host)
return proxy_bypass_registry(host)

def dict_to_sequence(d):
"""Returns an internal sequence dictionary update."""

if hasattr(d, 'items'):
d = d.items()

return d

def super_len(o):
total_length = None
current_position = 0

if hasattr(o, '__len__'):
total_length = len(o)

elif hasattr(o, 'len'):
total_length = o.len

elif hasattr(o, 'fileno'):
fileno = o.fileno()
except io.UnsupportedOperation:
total_length = os.fstat(fileno).st_size

# Having used fstat to determine the file length, we need to
# confirm that this file was opened up in binary mode.
if 'b' not in o.mode:
"Requests has determined the content-length for this "
"request using the binary size of the file: however, the "
"file has been opened in text mode (i.e. without the 'b' "
"flag in the mode). This may lead to an incorrect "
"content-length. In Requests 3.0, support will be removed "
"for files in text mode."),

if hasattr(o, 'tell'):
current_position = o.tell()
except (OSError, IOError):
# This can happen in some weird situations, such as when the file
# is actually a special file descriptor like stdin. In this
# instance, we don't know what the length is, so set it to zero and
# let requests chunk it instead.
if total_length is not None:
current_position = total_length
if hasattr(o, 'seek') and total_length is None:
# StringIO and BytesIO have seek but no useable fileno
# seek to end of file, 2)
total_length = o.tell()

# seek back to current position to support
# partially read file-like objects or 0)
except (OSError, IOError):
total_length = 0

if total_length is None:
total_length = 0

return max(0, total_length - current_position)

def get_netrc_auth(url, raise_errors=False):
"""Returns the Requests tuple auth for a given url from netrc."""

from netrc import netrc, NetrcParseError

netrc_path = None

for f in NETRC_FILES:
loc = os.path.expanduser('~/{0}'.format(f))
except KeyError:
# os.path.expanduser can fail when $HOME is undefined and
# getpwuid fails. See &

if os.path.exists(loc):
netrc_path = loc

# Abort early if there isn't one.
if netrc_path is None:

ri = urlparse(url)

# Strip port numbers from netloc. This weird `if...encode`` dance is
# used for Python 3.2, which doesn't support unicode literals.
splitstr = b':'
if isinstance(url, str):
splitstr = splitstr.decode('ascii')
host = ri.netloc.split(splitstr)[0]

_netrc = netrc(netrc_path).authenticators(host)
if _netrc:
# Return with login / password
login_i = (0 if _netrc[0] else 1)
return (_netrc[login_i], _netrc[2])
except (NetrcParseError, IOError):
# If there was a parsing error or a permissions issue reading the file,
# we'll just skip netrc auth unless explicitly asked to raise errors.
if raise_errors:

# AppEngine hackiness.
except (ImportError, AttributeError):

def guess_filename(obj):
"""Tries to guess the filename of the given object."""
name = getattr(obj, 'name', None)
if (name and isinstance(name, basestring) and name[0] != ' name[-1] != '>'):
return os.path.basename(name)

def from_key_val_list(value):
"""Take an object and test to see if it can be represented as a
dictionary. Unless it can not be represented as such, return an
OrderedDict, e.g.,


>>> from_key_val_list([('key', 'val')])
OrderedDict([('key', 'val')])
>>> from_key_val_list('string')
ValueError: need more than 1 value to unpack
>>> from_key_val_list({'key': 'val'})
OrderedDict([('key', 'val')])

:rtype: OrderedDict
if value is None:
return None

if isinstance(value, (str, bytes, bool, int)):
raise ValueError('cannot encode objects that are not 2-tuples')

return OrderedDict(value)

def to_key_val_list(value):
"""Take an object and test to see if it can be represented as a
dictionary. If it can be, return a list of tuples, e.g.,


>>> to_key_val_list([('key', 'val')])
[('key', 'val')]
>>> to_key_val_list({'key': 'val'})
[('key', 'val')]
>>> to_key_val_list('string')
ValueError: cannot encode objects that are not 2-tuples.

:rtype: list
if value is None:
return None

if isinstance(value, (str, bytes, bool, int)):
raise ValueError('cannot encode objects that are not 2-tuples')

if isinstance(value, collections.Mapping):
value = value.items()

return list(value)

# From mitsuhiko/werkzeug (used with permission).
def parse_list_header(value):
"""Parse lists as described by RFC 2068 Section 2.

In particular, parse comma-separated lists where the elements of
the list may include quoted-strings. A quoted-string could
contain a comma. A non-quoted string could have quotes in the
middle. Quotes are removed automatically after parsing.

It basically works like :func:`parse_set_header` just that items
may appear multiple times and case sensitivity is preserved.

The return value is a standard :class:`list`:

>>> parse_list_header('token, "quoted value"')
['token', 'quoted value']

To create a header from the :class:`list` again, use the
:func:`dump_header` function.

:param value: a string with a list header.
:return: :class:`list`
:rtype: list
result = []
for item in _parse_list_header(value):
if item[:1] == item[-1:] == '"':
item = unquote_header_value(item[1:-1])
return result

# From mitsuhiko/werkzeug (used with permission).
def parse_dict_header(value):
"""Parse lists of key, value pairs as described by RFC 2068 Section 2 and
convert them into a python dict:

>>> d = parse_dict_header('foo="is a fish", bar="as well"')
>>> type(d) is dict
>>> sorted(d.items())
[('bar', 'as well'), ('foo', 'is a fish')]

If there is no value for a key it will be `None`:

>>> parse_dict_header('key_without_value')
{'key_without_value': None}

To create a header from the :class:`dict` again, use the
:func:`dump_header` function.

:param value: a string with a dict header.
:return: :class:`dict`
:rtype: dict
result = {}
for item in _parse_list_header(value):
if '=' not in item:
result[item] = None
name, value = item.split('=', 1)
if value[:1] == value[-1:] == '"':
value = unquote_header_value(value[1:-1])
result[name] = value
return result

# From mitsuhiko/werkzeug (used with permission).
def unquote_header_value(value, is_filename=False):
r"""Unquotes a header value. (Reversal of :func:`quote_header_value`).
This does not use the real unquoting but what browsers are actually
using for quoting.

:param value: the header value to unquote.
:rtype: str
if value and value[0] == value[-1] == '"':
# this is not the real unquoting, but fixing this so that the
# RFC is met will result in bugs with internet explorer and
# probably some other browsers as well. IE for example is
# uploading files with "C:\foo\bar.txt" as filename
value = value[1:-1]

# if this is a filename and the starting characters look like
# a UNC path, then just return the value without quotes. Using the
# replace sequence below on a UNC path has the effect of turning
# the leading double slash into a single slash and then
# _fix_ie_filename() doesn't work correctly. See #458.
if not is_filename or value[:2] != '\\\\':
return value.replace('\\\\', '\\').replace('\\"', '"')
return value

def dict_from_cookiejar(cj):
"""Returns a key/value dictionary from a CookieJar.

:param cj: CookieJar object to extract cookies from.
:rtype: dict

cookie_dict = {}

for cookie in cj:
cookie_dict[] = cookie.value

return cookie_dict

def add_dict_to_cookiejar(cj, cookie_dict):
"""Returns a CookieJar from a key/value dictionary.

:param cj: CookieJar to insert cookies into.
:param cookie_dict: Dict of key/values to insert into CookieJar.
:rtype: CookieJar

return cookiejar_from_dict(cookie_dict, cj)

def get_encodings_from_content(content):
"""Returns encodings from given content string.

:param content: bytestring to extract encodings from.
'In requests 3.0, get_encodings_from_content will be removed. For '
'more information, please see the discussion on issue #2266. (This'
' warning should only appear once.)'),

charset_re = re.compile(r']', flags=re.I)
pragma_re = re.compile(r']', flags=re.I)
xml_re = re.compile(r'^]')

return (charset_re.findall(content) +
pragma_re.findall(content) +

def get_encoding_from_headers(headers):
"""Returns encodings from given HTTP Header Dict.

:param headers: dictionary to extract encoding from.
:rtype: str

content_type = headers.get('content-type')

if not content_type:
return None

content_type, params = cgi.parse_header(content_type)

if 'charset' in params:
return params['charset'].strip("'\"")

if 'text' in content_type:
return 'ISO-8859-1'

def stream_decode_response_unicode(iterator, r):
"""Stream decodes a iterator."""

if r.encoding is None:
for item in iterator:
yield item

decoder = codecs.getincrementaldecoder(r.encoding)(errors='replace')
for chunk in iterator:
rv = decoder.decode(chunk)
if rv:
yield rv
rv = decoder.decode(b'', final=True)
if rv:
yield rv

def iter_slices(string, slice_length):
"""Iterate over slices of a string."""
pos = 0
if slice_length is None or slice_length slice_length = len(string)
while pos yield string[pos:pos + slice_length]
pos += slice_length

def get_unicode_from_response(r):
"""Returns the requested content back in unicode.

:param r: Response object to get unicode content from.


1. charset from content-type
2. fall back and replace all unicode characters

:rtype: str
'In requests 3.0, get_unicode_from_response will be removed. For '
'more information, please see the discussion on issue #2266. (This'
' warning should only appear once.)'),

tried_encodings = []

# Try charset from content-type
encoding = get_encoding_from_headers(r.headers)

if encoding:
return str(r.content, encoding)
except UnicodeError:

# Fall back:
return str(r.content, encoding, errors='replace')
except TypeError:
return r.content

# The unreserved URI characters (RFC 3986)
UNRESERVED_SET = frozenset(
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" + "0123456789-._~")

def unquote_unreserved(uri):
"""Un-escape any percent-escape sequences in a URI that are unreserved
characters. This leaves all reserved, illegal and non-ASCII bytes encoded.

:rtype: str
parts = uri.split('%')
for i in range(1, len(parts)):
h = parts[i][0:2]
if len(h) == 2 and h.isalnum():
c = chr(int(h, 16))
except ValueError:
raise InvalidURL("Invalid percent-escape sequence: '%s'" % h)

parts[i] = c + parts[i][2:]
parts[i] = '%' + parts[i]
parts[i] = '%' + parts[i]
return ''.join(parts)

def requote_uri(uri):
"""Re-quote the given URI.

This function passes the given URI through an unquote/quote cycle to
ensure that it is fully and consistently quoted.

:rtype: str
safe_with_percent = "!#$%&'()*+,/:;[email protected][]~"
safe_without_percent = "!#$&'()*+,/:;[email protected][]~"
# Unquote only the unreserved characters
# Then quote only illegal characters (do not quote reserved,
# unreserved, or '%')
return quote(unquote_unreserved(uri), safe=safe_with_percent)
except InvalidURL:
# We couldn't unquote the given URI, so let's try quoting it, but
# there may be unquoted '%'s in the URI. We need to make sure they're
# properly quoted so they do not cause issues elsewhere.
return quote(uri, safe=safe_without_percent)

def address_in_network(ip, net):
"""This function allows you to check if an IP belongs to a network subnet

Example: returns True if ip = and net =
returns False if ip = and net =

:rtype: bool
ipaddr = struct.unpack('=L', socket.inet_aton(ip))[0]
netaddr, bits = net.split('/')
netmask = struct.unpack('=L', socket.inet_aton(dotted_netmask(int(bits))))[0]
network = struct.unpack('=L', socket.inet_aton(netaddr))[0] & netmask
return (ipaddr & netmask) == (network & netmask)

def dotted_netmask(mask):
"""Converts mask from /xx format to

Example: if mask is 24 function returns

:rtype: str
bits = 0xffffffff ^ (1 return socket.inet_ntoa(struct.pack('>I', bits))

def is_ipv4_address(string_ip):
:rtype: bool
except socket.error:
return False
return True

def is_valid_cidr(string_network):
Very simple check of the cidr format in no_proxy variable.

:rtype: bool
if string_network.count('/') == 1:
mask = int(string_network.split('/')[1])
except ValueError:
return False

if mask 32:
return False

except socket.error:
return False
return False
return True

def set_environ(env_name, value):
"""Set the environment variable 'env_name' to 'value'

Save previous value, yield, and then restore the previous value stored in
the environment variable 'env_name'.

If 'value' is None, do nothing"""
value_changed = value is not None
if value_changed:
old_value = os.environ.get(env_name)
os.environ[env_name] = value
if value_changed:
if old_value is None:
del os.environ[env_name]
os.environ[env_name] = old_value

def should_bypass_proxies(url, no_proxy):
Returns whether we should bypass proxies or not.

:rtype: bool
get_proxy = lambda k: os.environ.get(k) or os.environ.get(k.upper())

# First check whether no_proxy is defined. If it is, check that the URL
# we're getting isn't in the no_proxy list.
no_proxy_arg = no_proxy
if no_proxy is None:
no_proxy = get_proxy('no_proxy')
netloc = urlparse(url).netloc

if no_proxy:
# We need to check whether we match here. We need to see if we match
# the end of the netloc, both with and without the port.
no_proxy = (
host for host in no_proxy.replace(' ', '').split(',') if host

ip = netloc.split(':')[0]
if is_ipv4_address(ip):
for proxy_ip in no_proxy:
if is_valid_cidr(proxy_ip):
if address_in_network(ip, proxy_ip):
return True
elif ip == proxy_ip:
# If no_proxy ip was defined in plain IP notation instead of cidr notation &
# matches the IP of the index
return True
for host in no_proxy:
if netloc.endswith(host) or netloc.split(':')[0].endswith(host):
# The URL does match something in no_proxy, so we don't want
# to apply the proxies on this URL.
return True

# If the system proxy settings indicate that this URL should be bypassed,
# don't proxy.
# The proxy_bypass function is incredibly buggy on OS X in early versions
# of Python 2.6, so allow this call to fail. Only catch the specific
# exceptions we've seen, though: this call failing in other ways can reveal
# legitimate problems.
with set_environ('no_proxy', no_proxy_arg):
bypass = proxy_bypass(netloc)
except (TypeError, socket.gaierror):
bypass = False

if bypass:
return True

return False

def get_environ_proxies(url, no_proxy=None):
Return a dict of environment proxies.

:rtype: dict
if should_bypass_proxies(url, no_proxy=no_proxy):
return {}
return getproxies()

def select_proxy(url, proxies):
"""Select a proxy for the url, if applicable.

:param url: The url being for the request
:param proxies: A dictionary of schemes or schemes and hosts to proxy URLs
proxies = proxies or {}
urlparts = urlparse(url)
if urlparts.hostname is None:
return proxies.get(urlparts.scheme, proxies.get('all'))

proxy_keys = [
urlparts.scheme + '://' + urlparts.hostname,
'all://' + urlparts.hostname,
proxy = None
for proxy_key in proxy_keys:
if proxy_key in proxies:
proxy = proxies[proxy_key]

return proxy

def default_user_agent(name="python-requests"):
Return a string representing the default user agent.

:rtype: str
return '%s/%s' % (name, __version__)

def default_headers():
:rtype: requests.structures.CaseInsensitiveDict
return CaseInsensitiveDict({
'User-Agent': default_user_agent(),
'Accept-Encoding': ', '.join(('gzip', 'deflate')),
'Accept': '*/*',
'Connection': 'keep-alive',

def parse_header_links(value):
"""Return a dict of parsed link headers proxies.

i.e. Link: ; rel=front; type="image/jpeg",; rel=back;type="image/jpeg"

:rtype: list

links = []

replace_chars = ' \'"'

for val in re.split(', * try:
url, params = val.split(';', 1)
except ValueError:
url, params = val, ''

link = {'url': url.strip(' \'"')}

for param in params.split(';'):
key, value = param.split('=')
except ValueError:

link[key.strip(replace_chars)] = value.strip(replace_chars)


return links

# Null bytes; no need to recreate these on each call to guess_json_utf
_null = '\x00'.encode('ascii') # encoding to ASCII for Python 3
_null2 = _null * 2
_null3 = _null * 3

def guess_json_utf(data):
:rtype: str
# JSON always starts with two ASCII characters, so detection is as
# easy as counting the nulls and from their location and count
# determine the encoding. Also detect a BOM, if present.
sample = data[:4]
if sample in (codecs.BOM_UTF32_LE, codecs.BOM_UTF32_BE):
return 'utf-32' # BOM included
if sample[:3] == codecs.BOM_UTF8:
return 'utf-8-sig' # BOM included, MS style (discouraged)
if sample[:2] in (codecs.BOM_UTF16_LE, codecs.BOM_UTF16_BE):
return 'utf-16' # BOM included
nullcount = sample.count(_null)
if nullcount == 0:
return 'utf-8'
if nullcount == 2:
if sample[::2] == _null2: # 1st and 3rd are null
return 'utf-16-be'
if sample[1::2] == _null2: # 2nd and 4th are null
return 'utf-16-le'
# Did not detect 2 valid UTF-16 ascii-range characters
if nullcount == 3:
if sample[:3] == _null3:
return 'utf-32-be'
if sample[1:] == _null3:
return 'utf-32-le'
# Did not detect a valid UTF-32 ascii-range character
return None

def prepend_scheme_if_needed(url, new_scheme):
"""Given a URL that may or may not have a scheme, prepend the given scheme.
Does not replace a present scheme with the one provided as an argument.

:rtype: str
scheme, netloc, path, params, query, fragment = urlparse(url, new_scheme)

# urlparse is a finicky beast, and sometimes decides that there isn't a
# netloc present. Assume that it's being over-cautious, and switch netloc
# and path if urlparse decided there was no netloc.
if not netloc:
netloc, path = path, netloc

return urlunparse((scheme, netloc, path, params, query, fragment))

def get_auth_from_url(url):
"""Given a url with authentication components, extract them into a tuple of

:rtype: (str,str)
parsed = urlparse(url)

auth = (unquote(parsed.username), unquote(parsed.password))
except (AttributeError, TypeError):
auth = ('', '')

return auth

# Moved outside of function to avoid recompile every call
_CLEAN_HEADER_REGEX_BYTE = re.compile(b'^\\S[^\\r\\n]*$|^$')
_CLEAN_HEADER_REGEX_STR = re.compile(r'^\S[^\r\n]*$|^$')

def check_header_validity(header):
"""Verifies that header value is a string which doesn't contain
leading whitespace or return characters. This prevents unintended
header injection.

:param header: tuple, in the format (name, value).
name, value = header

if isinstance(value, bytes):
if not pat.match(value):
raise InvalidHeader("Invalid return character or leading space in header: %s" % name)
except TypeError:
raise InvalidHeader("Value for header {%s: %s} must be of type str or "
"bytes, not %s" % (name, value, type(value)))

def urldefragauth(url):
Given a url remove the fragment and the authentication part.

:rtype: str
scheme, netloc, path, params, query, fragment = urlparse(url)

# see func:`prepend_scheme_if_needed`
if not netloc:
netloc, path = path, netloc

netloc = netloc.rsplit('@', 1)[-1]

return urlunparse((scheme, netloc, path, params, query, ''))

def rewind_body(prepared_request):
"""Move file pointer back to its recorded starting position
so it can be read again on redirect.
body_seek = getattr(prepared_request.body, 'seek', None)
if body_seek is not None and isinstance(prepared_request._body_position, integer_types):
except (IOError, OSError):
raise UnrewindableBodyError("An error occurred when rewinding request "
"body for redirect.")
raise UnrewindableBodyError("Unable to rewind request body for redirect.")

This post first appeared on Ricky's Python Notes, please read the originial post: here

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