由于您还没有定义空文件是什么:有些人也可能认为只有空行的文件是空文件。因此，如果你想检查你的文件是否只包含空行(任何空白字符，'\r'， '\n'， '\t')，你可以按照下面的例子:

Python 3

import re

def whitespace_only(file):
    content = open(file, 'r').read()
    if re.search(r'^\s*$', content):
        return True

解释:上面的例子使用正则表达式(regex)来匹配文件的内容(content)。

具体来说:^\s*$作为一个整体意味着如果文件只包含空行和/或空格。

^在一行的开始处断言位置 s匹配任何空白字符(等于[\r\n\t\f\v]) *量词-在0和无限次之间匹配，尽可能多的次数，根据需要反馈(贪婪) $在一行的末尾断言位置

如果出于某种原因，你已经打开了文件，你可以尝试这样做:

>>> with open('New Text Document.txt') as my_file:
...     # I already have file open at this point.. now what?
...     my_file.seek(0) # Ensure you're at the start of the file..
...     first_char = my_file.read(1) # Get the first character
...     if not first_char:
...         print "file is empty" # The first character is the empty string..
...     else:
...         my_file.seek(0) # The first character wasn't empty. Return to the start of the file.
...         # Use file now
...
file is empty

import os    
os.path.getsize(fullpathhere) > 0

结合ghostdog74的回答和评论:

>>> import os
>>> os.stat('c:/pagefile.sys').st_size==0
False

False表示非空文件。

让我们写一个函数:

import os

def file_is_empty(path):
    return os.stat(path).st_size==0

将JSON追加到文件的完整示例

可重用的功能

import json
import os 

def append_json_to_file(filename, new_data):
    """ If filename does not exist """
    data = []
    if not os.path.isfile(filename):
        data.append(new_data)
        with open(filename, 'w') as f:
            f.write(json.dumps(data))
    else:
        """ If filename exists but empty """
        if os.stat(filename).st_size == 0:
            data = []
            with open(filename, 'w') as f:
                f.write(json.dumps(data))
        """ If filename exists """
        with open(filename, 'r+') as f:
            file_data = json.load(f)
            file_data.append(new_data)
            f.seek(0)
            json.dump(file_data, f)

运行它

filename = './exceptions.json'
append_json_to_file(filename, {
    'name': 'LVA',
    'age': 22
})
append_json_to_file(filename, {
    'name': 'CSD',
    'age': 20
})        

结果

[{"name": "LVA", "age": 22}, {"name": "CSD", "age": 20}]

如果您有文件对象，那么

>>> import os
>>> with open('new_file.txt') as my_file:
...     my_file.seek(0, os.SEEK_END) # go to end of file
...     if my_file.tell(): # if current position is truish (i.e != 0)
...         my_file.seek(0) # rewind the file for later use 
...     else:
...         print "file is empty"
... 
file is empty