Free Exchange Rate API Python
Guide with Working Code用 Python 免费汇率 API
获取并转换汇率

Free exchange rate API Python: the practical pathPython 免费汇率 API：实用实现路径

How to choose a free currency exchange rate API如何选择免费的货币汇率接口

“Free” can mean an open public endpoint or a limited free plan. Before using any provider, verify whether an API key is required, how often rates refresh, which currencies and dates are available, and whether the terms permit your intended use.

“免费”可能指开放公共接口，也可能只是有限额度。接入前要核对是否需要 API Key、更新频率、币种与日期覆盖、请求配额，以及许可是否适合你的用途。

Free exchange rate API without an API key无需 API Key 的免费汇率接口

A no-key endpoint is convenient for a prototype, but it still needs timeouts, caching, respectful request volume, and a fallback plan. Frankfurter documents a public, open-source API with no API key and daily central-bank-derived rates.

免 Key 接口适合原型，但仍应设置超时、缓存、合理请求频率和降级方案。Frankfurter 的官方文档说明其公共开源接口无需 API Key，并提供央行来源的日度汇率。

Public API, free tier, or paid market feed?公共 API、免费套餐还是付费行情？

Choose a public reference-rate API for prototypes, reporting, analytics, and low-frequency price localization. A registered free tier may offer broader currency coverage or more frequent updates, but introduces key rotation and quota monitoring. Trading, settlement, compliance, or customer-facing quotes may require a licensed market-data feed with explicit service levels.

公共参考汇率 API 适合原型、报表、分析和低频价格本地化。需要注册的免费套餐可能覆盖更多币种或提高更新频率，但也带来密钥轮换和配额监控。交易、结算、合规或面向客户的报价，通常需要具有明确授权和服务等级的市场数据源。

Questions to answer before integration接入前必须回答的问题

• Does the source publish reference, mid-market, buy, sell, or executable rates?
• Which timezone defines the response date, and how are weekends handled?
• Can the base currency change, or must cross-rates be calculated locally?
• Are attribution, caching, redistribution, or commercial-use restrictions present?

• 数据是参考价、中间价、买入价、卖出价，还是可成交报价？
• 响应日期采用哪个时区，周末和节假日如何处理？
• 能否切换基准币，还是需要在本地计算交叉汇率？
• 是否存在署名、缓存、再分发或商业使用限制？

Get live exchange rates in Python with requests用 requests 在 Python 中获取最新汇率

The example uses a documented single-pair endpoint. “Latest” means the provider's latest published reference rate; inspect the returned date and provider information instead of assuming tick-by-tick market data.

下面使用文档公开的单一货币对接口。“最新”指服务商最近发布的参考汇率，应检查响应日期和来源，不要把它当成逐笔实时行情。

from dataclasses import dataclass
from datetime import date
from decimal import Decimal, InvalidOperation

import requests
from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry


@dataclass(frozen=True)
class RateObservation:
    observed_on: date
    base: str
    quote: str
    rate: Decimal


def build_session() -> requests.Session:
    retry = Retry(
        total=4,
        connect=3,
        read=3,
        status=3,
        backoff_factor=0.5,
        status_forcelist=(429, 500, 502, 503, 504),
        allowed_methods=frozenset({"GET"}),
        respect_retry_after_header=True,
        raise_on_status=False,
    )
    session = requests.Session()
    session.mount("https://", HTTPAdapter(max_retries=retry))
    return session


def get_rate(
    session: requests.Session,
    base: str = "USD",
    quote: str = "EUR",
) -> RateObservation:
    base, quote = base.upper(), quote.upper()
    if not (len(base) == len(quote) == 3 and base.isalpha() and quote.isalpha()):
        raise ValueError("Currency codes must contain three letters")

    url = f"https://api.frankfurter.dev/v2/rate/{base}/{quote}"
    response = session.get(url, timeout=(3.05, 10))
    response.raise_for_status()
    data = response.json()

    required = {"date", "base", "quote", "rate"}
    if not required <= data.keys():
        raise ValueError("Unexpected exchange-rate response")
    if data["base"] != base or data["quote"] != quote:
        raise ValueError("Provider returned a different currency pair")

    try:
        observed_on = date.fromisoformat(data["date"])
        value = Decimal(str(data["rate"]))
    except (TypeError, ValueError, InvalidOperation) as exc:
        raise ValueError("Invalid date or exchange rate") from exc
    if not value.is_finite() or value <= 0:
        raise ValueError("Exchange rate must be a positive finite number")

    return RateObservation(observed_on, base, quote, value)


session = build_session()
rate = get_rate(session, "USD", "EUR")
print(rate.observed_on, rate.rate)

Handle timeouts, HTTP errors, and malformed JSON处理超时、HTTP 错误和异常 JSON

Catch requests.Timeout, requests.HTTPError, and requests.JSONDecodeError separately. Log the provider, pair, status, and timestamp without exposing credentials. Retry only transient failures with backoff.

分别处理 requests.Timeout、requests.HTTPError 和 requests.JSONDecodeError。记录服务商、货币对、状态和时间，但不要泄露密钥；只对临时故障执行退避重试。

Convert currency amounts in Python在 Python 中换算货币金额

For a single-pair response, multiply the amount by the returned rate and use Decimal with an explicit rounding rule when money is displayed or stored. Keep the original rate, timestamp, and source for auditability.

对单一货币对响应，用金额乘以返回汇率。展示或存储金额时使用 Decimal 并明确舍入规则，同时保存原始汇率、时间戳和来源，便于审计。

from decimal import Decimal, ROUND_HALF_UP

def convert_amount(amount, rate, minor_units=2):
    value = Decimal(str(amount)) * Decimal(str(rate))
    quantum = Decimal("1").scaleb(-minor_units)
    return value.quantize(quantum, rounding=ROUND_HALF_UP)

converted = convert_amount("125.50", rate.rate)
print(f"125.50 USD = {converted} EUR")

Use a session, retry only transient failures复用 Session，只重试临时故障

The shared requests.Session reuses connections. Its adapter retries connection and read failures, HTTP 429, and selected 5xx responses with bounded exponential backoff, while respect_retry_after_header=True follows server-supplied waiting guidance. Invalid currency codes and other deterministic 4xx responses are not retried. Keep attempts bounded so a dependency problem cannot consume every application worker.

共享的 requests.Session 会复用连接。适配器只对连接或读取故障、HTTP 429 和部分 5xx 响应执行有次数上限的指数退避；respect_retry_after_header=True 会遵守服务端给出的等待时间。无效币种等确定性的 4xx 错误不会重试。必须限制尝试次数，避免外部依赖故障耗尽应用工作线程。

Exchange-rate direction, cross rates, and money rounding汇率方向、交叉汇率与金额舍入

Define every rate as units of quote currency per one unit of base currency. If USD/EUR = 0.92, one U.S. dollar converts to 0.92 euros; the inverse EUR/USD is 1 / 0.92, not 0.92. Preserve the provider's stated pair and never infer direction from a field name such as rate alone.

应把每个汇率定义为“1 单位基准币可兑换多少单位目标币”。如果 USD/EUR = 0.92，表示 1 美元可兑换 0.92 欧元；反向的 EUR/USD 应为 1 ÷ 0.92，不能仍写成 0.92。必须保存供应商返回的货币对方向，不能只凭一个名为 rate 的字段猜测。

Fetch historical exchange rates with Python用 Python 获取历史汇率数据

Historical endpoints commonly accept a date or date range. Validate ISO currency codes and dates before the request, then decide how weekends, holidays, missing observations, and provider revisions should be represented in your application.

历史接口通常接收日期或日期范围。请求前校验 ISO 币种代码和日期，并明确周末、节假日、缺失值及服务商修订在应用中的处理方式。

Cache rates without serving stale data silently缓存汇率但不要静默返回过期数据

Store the source date next to the value, set cache expiry from the provider's publication cadence, and surface stale status to callers. For production, monitor failures and keep a last-known-good value with a clear age.

把来源日期和汇率一起存储，按服务商发布节奏设置过期时间，并向调用方明确标记陈旧状态。生产环境应监控失败，并保留带明确年龄的最后有效值。

Build a time series without hidden gaps构建不隐藏缺口的汇率时间序列

Keep the provider date as the observation key rather than replacing it with the request time. Store missing dates explicitly or document forward-fill rules. When comparing providers, normalize base currency, timezone, decimal precision, and holiday calendars before calculating returns or averages.

应使用服务商返回的日期作为观测键，不要用请求时间替代。对缺失日期进行明确记录，或清楚说明向前填充规则。比较不同数据源前，需要统一基准币、时区、小数精度和节假日日历，再计算收益率或平均值。

Production checklist for a Python exchange rate integrationPython 汇率集成的生产检查清单

A successful HTTP 200 response is only the first check. Production code should verify schema, currency pair, source date, numeric range, cache age, and provider identity before a rate reaches pricing or reporting logic.

HTTP 200 只代表请求成功。汇率进入定价或报表逻辑前，生产代码还应验证响应结构、货币对、来源日期、数值范围、缓存年龄和服务商身份。

Test cases worth automating值得自动化的测试用例

• Valid latest and historical responses with fixed fixtures.
• Timeout, connection reset, 429, 500, malformed JSON, and missing fields.
• Unsupported currency codes, same-currency conversion, zero and negative amounts.
• Weekend dates, stale cache, provider date changes, and rounding for different minor units.

• 使用固定样本测试最新与历史汇率的正常响应。
• 测试超时、连接重置、429、500、异常 JSON 和缺失字段。
• 测试不支持的币种、同币种换算、零金额和负金额。
• 测试周末日期、陈旧缓存、服务商日期变化及不同最小货币单位的舍入。

How QVeris helps Python apps find exchange rate capabilitiesQVeris 如何帮助 Python 应用查找汇率能力

• Discover exchange-rate and currency-data capabilities by task.
• Inspect inputs and outputs before integrating a provider.
• Keep provider claims separate from application-level reliability checks.

• 按任务发现汇率与货币数据能力。
• 接入前检查输入、输出和调用要求。
• 区分服务商声明与应用自身的可靠性验证。

Free exchange rate API Python FAQPython 免费汇率 API 常见问题

Authoritative references权威参考