如何将含数组的Python字典JSON序列化并内联数组写入文件

There are two straightforward approaches to achieve this, depending on whether you want compact JSON or indented (human-readable) JSON with inline arrays.

Approach 1: Compact JSON (No Indentation, All Inline) #

If you don’t need hierarchical indentation and just want all content (including arrays) to be in a compact, single-line format, use the separators parameter in json.dump() or json.dumps():

import json

# Your dictionary data
your_dict = {
    '#charliehebdo_attack_paris-20150107_072714-20150107_085144': {
        'OWA_max': 0.57489770154717,
        'features': [0.57489770154717, 0.3087177211515125, 0.30136460335548143, ...],
        'truth': 1.0,
        'weights': [1, 0, 0, 0, ...]
    }
}

# Write to file with compact formatting
with open('output_compact.json', 'w', encoding='utf-8') as f:
    json.dump(your_dict, f, separators=(',', ': '), ensure_ascii=False)

Why this works: #

• The separators=(',', ': ') parameter removes extra whitespace between elements, forcing arrays to stay inline.
• ensure_ascii=False preserves any non-ASCII characters in your keys/values (safe to use even if you don’t have them).

Approach 2: Indented JSON with Inline Arrays #

If you want the dictionary hierarchy to be indented for readability but keep arrays inline, serialize normally first, then post-process the JSON string to collapse array blocks:

import json
import re

# Your dictionary data
your_dict = {
    '#charliehebdo_attack_paris-20150107_072714-20150107_085144': {
        'OWA_max': 0.57489770154717,
        'features': [0.57489770154717, 0.3087177211515125, ...],
        'truth': 1.0,
        'weights': [1, 0, 0, ...]
    }
}

# Step 1: Serialize with indentation for readability
json_str = json.dumps(your_dict, indent=2, ensure_ascii=False)

# Step 2: Collapse arrays into single lines using regex
processed_json = re.sub(
    r'\[\s*(.*?)\s*\]',
    lambda match: '[' + match.group(1).replace('\n', '').replace('  ', ' ').strip().replace(' ,', ',') + ']',
    json_str,
    flags=re.DOTALL
)

# Step 3: Write the processed JSON to file
with open('output_indented.json', 'w', encoding='utf-8') as f:
    f.write(processed_json)

Why this works: #

• json.dumps(..., indent=2) creates a human-readable structure with indented keys.
• The regex matches multi-line array blocks, removes newlines and excess whitespace, and collapses them into a single line.
• The lambda function cleans up any leftover spacing issues (like accidental spaces before commas).

Bonus: Custom JSON Encoder (Advanced) #

For full control over serialization, you can subclass json.JSONEncoder to handle arrays inline while preserving indentation for dicts. This avoids post-processing and is great for large datasets:

import json

class InlineArrayEncoder(json.JSONEncoder):
    def __init__(self, indent=2, **kwargs):
        super().__init__(**kwargs)
        self.indent = indent
        self.current_indent = 0

    def encode(self, obj):
        if isinstance(obj, list):
            return '[' + ', '.join(self.encode(item) for item in obj) + ']'
        elif isinstance(obj, dict):
            self.current_indent += self.indent
            indent_str = '\n' + ' ' * self.current_indent
            items = [
                f'{self.encode(k)}:{indent_str}{self.encode(v)}'
                for k, v in obj.items()
            ]
            self.current_indent -= self.indent
            closing_indent = '\n' + ' ' * self.current_indent if self.current_indent > 0 else ''
            return '{' + indent_str + ','.join(items) + closing_indent + '}'
        else:
            return super().encode(obj)

# Usage
with open('output_custom.json', 'w', encoding='utf-8') as f:
    json.dump(your_dict, f, cls=InlineArrayEncoder, ensure_ascii=False)

内容的提问来源于stack exchange，提问作者ocram