zpljet

Official Python SDK for the ZPLJet API — fast ZPL → PDF/PNG conversion.

• Zero dependencies — a single small client on top of the stdlib
• Fully typed (py.typed) — parameters, results, and every API error code
• Reliable by default — automatic retries with exponential backoff (honoring Retry-After), per-request timeouts, typed exceptions
• Sync and async — ZplJet for scripts and servers, AsyncZplJet for asyncio code
• Python ≥ 3.10; tested through 3.14

Installation

Choose one:

pip install zpljet
uv add zpljet
poetry add zpljet

Quickstart

Create an API key in the dashboard (keys look like zpl_…), then:

import os
from pathlib import Path

from zpljet import ZplJet

zpljet = ZplJet(api_key=os.environ["ZPLJET_API_KEY"])

label = zpljet.convert(zpl="^XA^FO50,50^A0N,50,50^FDHello^FS^XZ")

Path("label.pdf").write_bytes(label.data)

Keep your API key server-side. Anyone with the key can spend your quota.

Usage

Convert to PDF or PNG

convert() accepts every parameter of POST /v1/convert:

label = zpljet.convert(
    zpl="^XA^FO50,50^A0N,50,50^FDHello^FS^XZ",
    format="png",     # "pdf" (default) | "png"
    dpmm=12,          # 6 | 8 (default, 203 dpi) | 12 (300 dpi) | 24 (600 dpi)
    width_mm=101.6,   # label width, default 4 in
    height_mm=152.4,  # label height, default 6 in
)

label.data          # bytes — the file
label.content_type  # "application/pdf" | "image/png"
label.id            # conversion id (shows up in your dashboard)

Hosted URLs (paid plans)

Pass output="url" to have ZPLJet host the file and return a public link instead of the bytes. Files are retained for your account's retention window (a dashboard setting, up to your plan's maximum).

hosted = zpljet.convert(zpl="^XA^FO50,50^A0N,50,50^FDHello^FS^XZ", output="url")

hosted.url             # public URL to the PDF (works until the file is deleted)
hosted.pages           # pages rendered (one per ^XA…^XZ block)
hosted.retention_days  # how long the file is kept
hosted.expires_at      # when the file is deleted and the URL stops working (ISO 8601, UTC)

The return type narrows automatically: output="url" gives a HostedLabel, everything else a LabelData.

Async

AsyncZplJet has the identical interface for asyncio code:

from zpljet import AsyncZplJet

zpljet = AsyncZplJet(api_key=os.environ["ZPLJET_API_KEY"])
label = await zpljet.convert(zpl="^XA^FO50,50^A0N,50,50^FDHello^FS^XZ")

The async client runs the dependency-free transport in a worker thread. Bound large batches with a semaphore; see examples/05_async_batch.py.

Error handling

Every API error code maps to a dedicated exception, so you branch with except — no string matching:

from zpljet import (
    ZplJet,
    APIConnectionError,
    BadRequestError,
    ConversionFailedError,
    QuotaExceededError,
    RateLimitError,
)

try:
    label = zpljet.convert(zpl=zpl)
except BadRequestError as err:
    print(f"Invalid request ({err.param}): {err.message}")
except QuotaExceededError as err:
    print(f"Quota used up ({err.used}/{err.quota}), resets {err.resets_at}")
except RateLimitError as err:
    print(f"Rate limited — retry after {err.retry_after}s")
except ConversionFailedError as err:
    print(f"Engine rejected the ZPL (conversion {err.conversion_id})")
except APIConnectionError as err:
    print(f"Network problem: {err}")

All of these extend ZplJetError, and every HTTP error carries status, code, doc_url, and the raw error payload in raw. Full code reference: zpljet.com/docs/errors.

Retries

Rate limits, transient 5xx responses, timeouts, and network failures retry up to twice by default. Retries use exponential backoff and honor Retry-After. conversion_failed is never retried.

# Client-wide
zpljet = ZplJet(api_key=key, max_retries=5)

# Or per request
zpljet.convert(zpl=zpl, max_retries=0)  # fail fast

Timeouts

Each attempt has a 60-second timeout by default:

zpljet = ZplJet(api_key=key, timeout=10.0)

# Per request:
zpljet.convert(zpl=zpl, timeout=5.0)

A timed-out attempt raises APITimeoutError (after retries).

Configuration

zpljet = ZplJet(
    api_key="zpl_…",                     # required
    base_url="https://api.zpljet.com",   # default
    timeout=60.0,                        # per-attempt timeout, seconds
    max_retries=2,                       # automatic retries
    transport=my_transport,              # custom transport (proxies, tests)
)

The default transport uses stdlib urllib. For connection pooling, inject any callable matching (url, body, headers, timeout) -> TransportResponse.

Examples

Runnable scripts live in examples/:

ZPLJET_API_KEY=zpl_… python examples/01_convert_to_pdf.py

Contributing & development

python -m venv .venv && source .venv/bin/activate
pip install -e ".[dev]"

ruff check .
mypy
pytest

ZPLJET_API_KEY=zpl_… pytest tests/test_e2e.py

License

MIT