如何检查是否存在文件,而不使用试用声明?
当前回答
要检查是否存在文件,
from sys import argv
from os.path import exists
script, filename = argv
target = open(filename)
print "file exists: %r" % exists(filename)
其他回答
>>> from pathlib import Path
>>> Path('/').is_file()
False
>>> Path('/initrd.img').is_file()
True
>>> Path('/doesnotexist').is_file()
False
>>> import os
>>> os.path.isfile('/')
False
>>> os.path.isfile('/initrd.img')
True
>>> os.path.isfile('/doesnotexist')
False
现在上面的可能是最好的实用直接答案在这里,但有可能有一个竞赛条件(取决于你正在尝试实现什么),并且事实上,基础实施使用一个尝试,但Python使用尝试到处在其实施。
更长、更有趣的答案
>>> from pathlib import Path
>>> root = Path('/')
>>> root.exists()
True
>>> root.is_file()
False
is_file(self)
Whether this path is a regular file (also True for symlinks pointing
to regular files).
>>> import tempfile
>>> file = tempfile.NamedTemporaryFile()
>>> filepathobj = Path(file.name)
>>> filepathobj.is_file()
True
>>> filepathobj.exists()
True
>>> del file
>>> filepathobj.exists()
False
>>> filepathobj.is_file()
False
def is_file(self):
"""
Whether this path is a regular file (also True for symlinks pointing
to regular files).
"""
try:
return S_ISREG(self.stat().st_mode)
except OSError as e:
if e.errno not in (ENOENT, ENOTDIR):
raise
# Path doesn't exist or is a broken symlink
# (see https://bitbucket.org/pitrou/pathlib/issue/12/)
return False
from contextlib import suppress
from pathlib import Path
>>> with suppress(OSError), Path('doesnotexist').open() as f:
... for line in f:
... print(line)
...
>>>
>>> with suppress(OSError):
... Path('doesnotexist').unlink()
...
>>>
class suppress(object):
def __init__(self, *exceptions):
self.exceptions = exceptions
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, traceback):
if exc_type is not None:
return issubclass(exc_type, self.exceptions)
from contextlib import contextmanager
@contextmanager
def suppress(*exceptions):
try:
yield
except exceptions:
pass
import os
os.path.isfile(path)
>>> OSError is os.error
True
try:
with open(path) as f:
f.read()
except OSError:
pass
import os
os.access(path, os.F_OK)
批评另一个答案:
另一个答案是关于os.access:
这个答案说,它更喜欢一个非皮顿,错误的方法,没有理由,似乎鼓励用户使用低级的API,而不理解它们。
它还创建了一个背景管理器,通过无条件返回真相,允许所有例外(包括键盘中断和系统输出!)沉默地通过,这是一个很好的方式来隐藏错误。
使用:
import os
# For testing purposes the arguments defaulted to the current folder and file.
# returns True if file found
def file_exists(FOLDER_PATH='../', FILE_NAME=__file__):
return os.path.isdir(FOLDER_PATH) \
and os.path.isfile(os.path.join(FOLDER_PATH, FILE_NAME))
它基本上是一个文件夹检查,然后使用 os.path.join 使用适当的目录分离器进行文件检查。
exist() and is_file() 对“路”对象的方法可以用来检查是否有一个特定的路径存在并是一个文件。
Python 3 程序检查是否存在文件:
# File name: check-if-file-exists.py
from pathlib import Path
filePath = Path(input("Enter path of the file to be found: "))
if filePath.exists() and filePath.is_file():
print("Success: File exists")
else:
print("Error: File does not exist")
出口:
$ python3 check-if-file-exists.py 输入文件的路径可以找到: /Users/macuser1/stack-overflow/index.html 成功: 文件存在 $ python3 check-if-file-exists.py 输入文件的路径可以找到: hghjg jghj 错误: 文件不存在
这就是我如何在一个文件夹中找到一个文件列表(在这些图像中)并在一个文件夹中搜索它(与子文件夹):
# This script concatenates JavaScript files into a unified JavaScript file to reduce server round-trips
import os
import string
import math
import ntpath
import sys
#import pyodbc
import gzip
import shutil
import hashlib
# BUF_SIZE is totally arbitrary, change for your app!
BUF_SIZE = 65536 # Let’s read stuff in 64 kilobyte chunks
# Iterate over all JavaScript files in the folder and combine them
filenames = []
shortfilenames = []
imgfilenames = []
imgshortfilenames = []
# Get a unified path so we can stop dancing with user paths.
# Determine where files are on this machine (%TEMP% directory and application installation directory)
if '.exe' in sys.argv[0]: # if getattr(sys, 'frozen', False):
RootPath = os.path.abspath(os.path.join(__file__, "..\\"))
elif __file__:
RootPath = os.path.abspath(os.path.join(__file__, "..\\"))
print ("\n storage of image files RootPath: %s\n" %RootPath)
FolderPath = "D:\\TFS-FARM1\\StoneSoup_STS\\SDLC\\Build\\Code\\StoneSoup_Refactor\\StoneSoupUI\\Images"
print ("\n storage of image files in folder to search: %s\n" %FolderPath)
for root, directories, filenames2 in os.walk(FolderPath):
for filename in filenames2:
fullname = os.path.join(root, filename)
filenames.append(fullname)
shortfilenames.append(filename)
for i, fname in enumerate(shortfilenames):
print("%s - %s" % (i+1, fname))
for root, directories, filenames2 in os.walk(RootPath):
for filename in filenames2:
fullname = os.path.join(root, filename)
imgfilenames.append(fullname)
imgshortfilenames.append(filename)
for i, fname in enumerate(imgshortfilenames):
print("%s - %s" % (i+1, fname))
for i, fname in enumerate(imgshortfilenames):
if fname in shortfilenames:
print("%s - %s exists" % (i+1, fname))
else:
print("%s - %s ABSENT" % (i+1, fname))
使用 os.path.exist 查看文件和目录:
import os.path
os.path.exists(file_path)
使用 os.path.isfile 仅查看文件(注:以下是符号链接):
os.path.isfile(file_path)
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