How to Convert decimal.Decimal to float in Various Python Data Structures

Example 1: Convert a single Decimal object

from decimal import Decimal
# 创建一个 Decimal 对象
decimal_value = Decimal('123.456')
# 转换为 float
float_value = float(decimal_value)
print(float_value)  # 输出: 123.456

Example 2: Convert Decimal objects in a list

from decimal import Decimal
# 创建一个包含 Decimal 对象的列表
decimal_list = [Decimal('1.1'), Decimal('2.2'), Decimal('3.3')]
# 转换为 float 列表
float_list = [float(d) for d in decimal_list]
print(float_list)  # 输出: [1.1, 2.2, 3.3]

Example 3: Convert Decimal objects in a dictionary

from decimal import Decimal
# 创建一个包含 Decimal 对象的字典
decimal_dict = {'a': Decimal('1.1'), 'b': Decimal('2.2'), 'c': Decimal('3.3')}
# 转换为 float 字典
float_dict = {k: float(v) for k, v in decimal_dict.items()}
print(float_dict)  # 输出: {'a': 1.1, 'b': 2.2, 'c': 3.3}

Example 4: Convert Decimal objects in a nested structure

from decimal import Decimal
# 创建一个包含 Decimal 对象的嵌套结构
nested_structure = {
    'key1': [Decimal('1.1'), Decimal('2.2')],
    'key2': {'subkey1': Decimal('3.3'), 'subkey2': Decimal('4.4')}
}

def convert_decimal_to_float(obj):
    if isinstance(obj, Decimal):
        return float(obj)
    elif isinstance(obj, dict):
        return {k: convert_decimal_to_float(v) for k, v in obj.items()}
    elif isinstance(obj, list):
        return [convert_decimal_to_float(item) for item in obj]
    else:
        return obj

float_structure = convert_decimal_to_float(nested_structure)
print(float_structure)  # 输出: {'key1': [1.1, 2.2], 'key2': {'subkey1': 3.3, 'subkey2': 4.4}}

Example 5: Convert Decimal objects in a pandas DataFrame

import pandas as pd
from decimal import Decimal
# 创建一个包含 Decimal 对象的 DataFrame
data = {
    'A': [Decimal('1.1'), Decimal('2.2')],
    'B': [Decimal('3.3'), Decimal('4.4')]
}
df = pd.DataFrame(data)
# 转换为 float DataFrame
float_df = df.applymap(lambda x: float(x) if isinstance(x, Decimal) else x)
print(float_df)  # 输出:
#          A    B
# 0  1.10000  3.3
# 1  2.20000  4.4

Example 6: Convert Decimal objects in a JSON string

import json
from decimal import Decimal
# 创建一个包含 Decimal 对象的 JSON 字符串
json_str = '{"a": 1.1, "b": 2.2}'
# 自定义 JSON 解析函数以处理 Decimal

def parse_decimal(dct):
    for key, value in dct.items():
        if isinstance(value, str) and '.' in value:
            try:
                dct[key] = float(Decimal(value))
            except Exception:
                pass
    return dct

parsed_dict = json.loads(json_str, object_hook=parse_decimal)
print(parsed_dict)  # 输出: {'a': 1.1, 'b': 2.2}

Example 7: Convert Decimal objects in a tuple

from decimal import Decimal
# 创建一个包含 Decimal 对象的元组
decimal_tuple = (Decimal('1.1'), Decimal('2.2'))
# 转换为 float 元组
float_tuple = tuple(float(d) for d in decimal_tuple)
print(float_tuple)  # 输出: (1.1, 2.2)

Example 8: Convert Decimal objects in a set

from decimal import Decimal
# 创建一个包含 Decimal 对象的集合
decimal_set = {Decimal('1.1'), Decimal('2.2'), Decimal('3.3')}
# 转换为 float 集合
float_set = {float(d) for d in decimal_set}
print(float_set)  # 输出: {1.1, 2.2, 3.3}

Example 9: Convert Decimal objects in a dictionary while preserving original types

from decimal import Decimal
# 创建一个包含 Decimal 对象的字典
decimal_dict = {'a': Decimal('1.1'), 'b': Decimal('2.2'), 'c': Decimal('3.3')}
# 转换为 float 字典（保持原始数据类型）

def convert_dict_decimal_to_float(d):
    return {k: float(v) if isinstance(v, Decimal) else v for k, v in d.items()}

float_dict = convert_dict_decimal_to_float(decimal_dict)
print(float_dict)  # 输出: {'a': 1.1, 'b': 2.2, 'c': 3.3}

Example 10: Convert Decimal objects in a list while preserving original types

from decimal import Decimal
# 创建一个包含 Decimal 对象的列表
decimal_list = [Decimal('1.1'), Decimal('2.2'), Decimal('3.3')]
# 转换为 float 列表（保持原始数据类型）

def convert_list_decimal_to_float(lst):
    return [float(item) if isinstance(item, Decimal) else item for item in lst]

float_list = convert_list_decimal_to_float(decimal_list)
print(float_list)  # 输出: [1.1, 2.2, 3.3]

Summary

The above examples show how to convert data of type decimal.Decimal to Python's float type and apply the conversion to various data structures; however, converting to float may lose precision, so avoid it in high‑precision calculations.