使用KuCoin API买入BTC时遇Funds increment invalid错误求助

我使用Python 3.12.3调用KuCoin API查询USDT余额并兑换为BTC，针对交易金额需匹配API提供的quoteIncrement倍数、以及价格波动问题，已设置0.01 USDT缓冲，并通过usdt_amount = (usdt_amount // quote_increment) * quote_increment调整金额，但执行时仍触发错误：

Order failed: 200-{"msg":"Funds increment invalid.","code":"400100"}

原代码如下：

from kucoin.client import Trade, User, Market

# Replace with your actual API credentials
api_key = 'my key'
api_secret = 'my secret'
api_passphrase = 'my passphrase'

# Initialize the KuCoin clients
trade_client = Trade(key=api_key, secret=api_secret, passphrase=api_passphrase)
user_client = User(key=api_key, secret=api_secret, passphrase=api_passphrase)
market_client = Market(key=api_key, secret=api_secret, passphrase=api_passphrase)

# Get account balances
account_balances = user_client.get_account_list()

# Find the USDT balance
usdt_balance = next((item for item in account_balances if item['currency'] == 'USDT' and item['type'] == 'trade'), None)

# Check if there is enough USDT balance
if usdt_balance and float(usdt_balance['balance']) > 0:
    total_usdt_amount = float(usdt_balance['balance'])
    buffer_amount = 0.01  # Leaving 0.01 USDT as buffer
    usdt_amount = total_usdt_amount - buffer_amount
    
    # Get the symbol info to find the quote increment and minimum size
    symbol_info = market_client.get_symbol_list()
    btc_usdt_info = next(item for item in symbol_info if item['symbol'] == 'BTC-USDT')
    quote_increment = float(btc_usdt_info['quoteIncrement'])
    quote_min_size = float(btc_usdt_info['quoteMinSize'])
    
    # Adjust USDT amount to be a multiple of quote_increment
    usdt_amount = (usdt_amount // quote_increment) * quote_increment

    if usdt_amount < quote_min_size:
        print(f"Order amount is too small, minimum required is {quote_min_size} USDT")
    else:
        # Create the market order to trade all USDT for BTC
        try:
            order = trade_client.create_market_order('BTC-USDT', 'buy', funds=str(usdt_amount))
            print(f"Order successful: Traded {usdt_amount} USDT for BTC")
        except Exception as e:
            print(f"Order failed: {e}")
else:
    print("Insufficient USDT balance or USDT balance not found")

问题原因及修复方案 #

1. 浮点数精度误差

Python的浮点数运算存在精度丢失问题，比如100.01 - 0.01理论上是100.0，但实际可能存储为99.99999999999999，后续的倍数调整无法完全修正这个误差，导致最终金额不符合quoteIncrement要求。

修复：使用decimal模块进行精确的小数运算，避免精度丢失：

from decimal import Decimal, getcontext

# 设置精度，匹配KuCoin的小数位数
getcontext().prec = 10

# 替换原金额计算部分
total_usdt_amount = Decimal(usdt_balance['balance'])
buffer_amount = Decimal('0.01')
usdt_amount = total_usdt_amount - buffer_amount

quote_increment = Decimal(btc_usdt_info['quoteIncrement'])
# 调整为quote_increment的倍数
usdt_amount = (usdt_amount // quote_increment) * quote_increment

2. 字符串格式化问题

将浮点数直接转为字符串时，可能出现多余的小数位（如100.0变成100.0000000001），KuCoin API无法识别这种格式。

修复：根据quoteIncrement的小数位数格式化字符串，比如BTC-USDT的quoteIncrement是0.01，则保留2位小数：

# 获取quoteIncrement的小数位数
decimal_places = len(quote_increment.split('.')[1]) if '.' in quote_increment else 0
# 格式化金额字符串
formatted_usdt_amount = f"{usdt_amount:.{decimal_places}f}"
# 传入API时使用格式化后的字符串
order = trade_client.create_market_order('BTC-USDT', 'buy', funds=formatted_usdt_amount)

3. 验证quoteIncrement的正确性

确认从get_symbol_list()获取的quoteIncrement值是否正确，比如BTC-USDT的quoteIncrement应为0.01，可以在代码中打印验证：

print(f"Quote Increment: {btc_usdt_info['quoteIncrement']}")

4. 缓冲后金额的边界检查

确保减去缓冲后的金额调整为倍数后，仍大于等于quoteMinSize，避免因缓冲导致金额过小。

修改后的完整代码 #

from kucoin.client import Trade, User, Market
from decimal import Decimal, getcontext

# Replace with your actual API credentials
api_key = 'my key'
api_secret = 'my secret'
api_passphrase = 'my passphrase'

# Initialize the KuCoin clients
trade_client = Trade(key=api_key, secret=api_secret, passphrase=api_passphrase)
user_client = User(key=api_key, secret=api_secret, passphrase=api_passphrase)
market_client = Market(key=api_key, secret=api_secret, passphrase=api_passphrase)

# Get account balances
account_balances = user_client.get_account_list()

# Find the USDT balance
usdt_balance = next((item for item in account_balances if item['currency'] == 'USDT' and item['type'] == 'trade'), None)

# Check if there is enough USDT balance
if usdt_balance and Decimal(usdt_balance['balance']) > 0:
    getcontext().prec = 10
    total_usdt_amount = Decimal(usdt_balance['balance'])
    buffer_amount = Decimal('0.01')  # Leaving 0.01 USDT as buffer
    usdt_amount = total_usdt_amount - buffer_amount
    
    # Get the symbol info to find the quote increment and minimum size
    symbol_info = market_client.get_symbol_list()
    btc_usdt_info = next(item for item in symbol_info if item['symbol'] == 'BTC-USDT')
    quote_increment_str = btc_usdt_info['quoteIncrement']
    quote_increment = Decimal(quote_increment_str)
    quote_min_size = Decimal(btc_usdt_info['quoteMinSize'])
    
    # Adjust USDT amount to be a multiple of quote_increment
    usdt_amount = (usdt_amount // quote_increment) * quote_increment

    if usdt_amount < quote_min_size:
        print(f"Order amount is too small, minimum required is {quote_min_size} USDT")
    else:
        # Format the amount to match quote increment's decimal places
        decimal_places = len(quote_increment_str.split('.')[1]) if '.' in quote_increment_str else 0
        formatted_usdt_amount = f"{usdt_amount:.{decimal_places}f}"
        # Create the market order to trade all USDT for BTC
        try:
            order = trade_client.create_market_order('BTC-USDT', 'buy', funds=formatted_usdt_amount)
            print(f"Order successful: Traded {formatted_usdt_amount} USDT for BTC")
        except Exception as e:
            print(f"Order failed: {e}")
else:
    print("Insufficient USDT balance or USDT balance not found")

内容的提问来源于stack exchange，提问作者Ramy Al Zuhouri