我有一个文本文件。我如何检查它是否为空?
当前回答
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
其他回答
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
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
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}]
如果文件不存在,getsize()和stat()都会抛出异常。这个函数将返回True/False而不抛出(更简单但不那么健壮):
import os
def is_non_zero_file(fpath):
return os.path.isfile(fpath) and os.path.getsize(fpath) > 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
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