modern-httplib2

A 100% compatible, zero-code-change drop-in replacement for Python's httplib2 library, powered under the hood by httpx and httpcore.

Why modern-httplib2?

Legacy httplib2 is deeply embedded across the Python ecosystem (notably via google-api-python-client, google-auth-httplib2, and multi-threaded tools like GAM), but its original transport layer is built directly on Python's low-level http.client with single-socket state per Http() instance.

modern-httplib2 keeps the exact httplib2 public API, module layout, exception hierarchy, RFC 2616 caching, authentication schemes (Basic, Digest, WSSE, GoogleLogin, HmacDigest), and ProxyInfo semantics while replacing the underlying transport engine with httpx (httpcore + h2):

• Python Package & PyPI Name: Published as modern-httplib2, importing as modern_httplib2.
• Transparent Interceptor / Auto-Patching: Providing import modern_httplib2.auto or modern_httplib2.patch() which mounts modern_httplib2 into sys.modules["httplib2"]. Existing dependencies like google-api-python-client and google-auth-httplib2 automatically and transparently use modern_httplib2 without any code changes to Google's libraries.
• Direct Import Support: Use directly via import modern_httplib2 or import modern_httplib2 as httplib2.
• Modern httpx / httpcore Transport: Uses httpx's httpcore connection pool and h11/h2 protocol state machines.
• True Multi-Threaded HTTP/2 Multiplexing: Multiple threads sharing a single Http() instance multiplex concurrent requests over a single TCP+TLS HTTP/2 connection (up to 100 concurrent streams per connection), even on cold start.
• Thread-Safe Connection Pooling: Unlike upstream httplib2.Http() (which is notorious for thread-safety crashes when shared across threads), modern-httplib2 uses thread-local active request dispatch backed by a thread-safe per-origin httpcore.ConnectionPool (pool_maxsize=16 by default).
• Transparent HTTP/2 over TLS (ALPN h2): Automatically negotiates HTTP/2 on HTTPS connections when the server advertises h2 via TLS ALPN, with seamless fallback to HTTP/1.1.
• Python 3.11+ Native: Built exclusively for supported Python versions (3.11+), free of legacy Python 2 / early Python 3 compatibility shims.
• 100% Upstream Test Suite Compatibility: Passes all 526+ upstream httplib2 unit and integration tests.

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Installation

Install from PyPI:

pip install modern-httplib2

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Usage

1. Transparent Interception in Existing Projects (e.g. GAM)

To automatically redirect all import httplib2 calls across your application and its dependencies (like google-api-python-client and google-auth-httplib2) to modern_httplib2, import modern_httplib2.auto at your application entrypoint:

try:
    import modern_httplib2.auto
except ImportError:
    pass

# All downstream imports now transparently use modern_httplib2!
import google_auth_httplib2
import googleapiclient.discovery
import httplib2

http = httplib2.Http()

2. Direct Import Usage

import modern_httplib2 as httplib2

http = httplib2.Http(".cache")
resp, content = http.request("https://httpbin.org/get", "GET")
print(resp.status, resp.version)  # e.g. 200, 20 (HTTP/2) or 11 (HTTP/1.1)

2. Thread-Safe Concurrent Requests

You can safely share a single httplib2.Http instance across multiple threads:

from concurrent.futures import ThreadPoolExecutor
import httplib2

http = httplib2.Http(pool_maxsize=16)

def fetch(url):
    resp, body = http.request(url)
    return resp.status, len(body)

with ThreadPoolExecutor(max_workers=8) as pool:
    results = list(pool.map(fetch, ["https://example.com"] * 32))

3. Controlling HTTP/2 Negotiation & Corporate Firewall Downgrade

HTTP/2 over TLS is enabled by default (enable_http2=True). For environments where corporate firewalls, deep packet inspection (DPI) middleboxes, or legacy proxies reject, reset, or misbehave with HTTP/2 traffic, modern-httplib2 provides multiple ways to force HTTP/1.1:

Automatic Firewall Fallback (Enabled by Default)

By default (auto_downgrade_http2=True), if an HTTP/2 connection fails due to a network or protocol reset (e.g. proxy RST on HTTP/2 preface, stream errors, or closed connections), modern-httplib2 will:

1. Automatically downgrade the connection to HTTP/1.1.
2. Remember that host for subsequent requests in the session.
3. Transparently retry the request without raising an exception to the caller.

Global / Application-Wide Toggle

Disable HTTP/2 globally in your application (for example, when a user sets force_http11 = true in their configuration file):

import httplib2

# Any of these can be called at startup:
httplib2.force_http11()
# or:
httplib2.ENABLE_HTTP2 = False
# or:
httplib2.set_enable_http2(False)

Environment Variable (Zero Code Change)

Set the environment variable in your shell or configuration:

export MODERN_HTTPLIB2_ENABLE_HTTP2=0
# or
export HTTPLIB2_ENABLE_HTTP2=0

Per-Instance Control

import httplib2

http_v1 = httplib2.Http(enable_http2=False)
# or dynamically on an existing instance:
http_v1.force_http11()

resp, content = http_v1.request("https://example.com")
assert resp.version == 11

4. Using with google-auth-httplib2

import google.auth
import google_auth_httplib2
import httplib2

credentials, project = google.auth.default(scopes=["https://www.googleapis.com/auth/cloud-platform"])
authed_http = google_auth_httplib2.AuthorizedHttp(credentials, http=httplib2.Http())
resp, content = authed_http.request("https://www.googleapis.com/oauth2/v1/ tokeninfo")

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Running Tests

.venv/bin/pytest