谁能告诉我怎么办？
答案 0 :(得分：76)
with open(filename) as f:
while True:
c = f.read(1)
if not c:
print "End of file"
break
print "Read a character:", c
答案 1 :(得分：32)
首先打开一个文件：
with open("filename") as fileobj:
for line in fileobj:
for ch in line:
print ch
答案 2 :(得分：14)
我喜欢接受的答案：它很简单，可以完成工作。我还想提供另一种实现方式：
def chunks(filename, buffer_size=4096):
"""Reads `filename` in chunks of `buffer_size` bytes and yields each chunk
until no more characters can be read; the last chunk will most likely have
less than `buffer_size` bytes.
:param str filename: Path to the file
:param int buffer_size: Buffer size, in bytes (default is 4096)
:return: Yields chunks of `buffer_size` size until exhausting the file
:rtype: str
"""
with open(filename, "rb") as fp:
chunk = fp.read(buffer_size)
while chunk:
yield chunk
chunk = fp.read(buffer_size)
def chars(filename, buffersize=4096):
"""Yields the contents of file `filename` character-by-character. Warning:
will only work for encodings where one character is encoded as one byte.
:param str filename: Path to the file
:param int buffer_size: Buffer size for the underlying chunks,
in bytes (default is 4096)
:return: Yields the contents of `filename` character-by-character.
:rtype: char
"""
for chunk in chunks(filename, buffersize):
for char in chunk:
yield char
def main(buffersize, filenames):
"""Reads several files character by character and redirects their contents
to `/dev/null`.
"""
for filename in filenames:
with open("/dev/null", "wb") as fp:
for char in chars(filename, buffersize):
fp.write(char)
if __name__ == "__main__":
# Try reading several files varying the buffer size
import sys
buffersize = int(sys.argv[1])
filenames = sys.argv[2:]
sys.exit(main(buffersize, filenames))
我建议的代码与您接受的答案基本相同：从文件中读取给定的字节数。不同之处在于它首先读取了大量数据（4006是X86的一个很好的默认值，但你可能想尝试1024或8192;你的页面大小的任何倍数），然后它产生那个块中的字符一个一个人。
我提供的代码对于较大的文件可能更快。举个例子，the entire text of War and Peace, by Tolstoy。这些是我的计时结果（使用OS X 10.7.4的Mac Book Pro; so.py是我给我粘贴的代码的名称）：
$ time python so.py 1 2600.txt.utf-8
python so.py 1 2600.txt.utf-8 3.79s user 0.01s system 99% cpu 3.808 total
$ time python so.py 4096 2600.txt.utf-8
python so.py 4096 2600.txt.utf-8 1.31s user 0.01s system 99% cpu 1.318 total
现在：不要将4096的缓冲区大小作为普遍真理;看看我得到的不同大小的结果（缓冲区大小（字节）与墙上时间（秒））：
2 2.726
4 1.948
8 1.693
16 1.534
32 1.525
64 1.398
128 1.432
256 1.377
512 1.347
1024 1.442
2048 1.316
4096 1.318
正如你所看到的，你可以早些开始看到收益（我的时间可能非常不准确）;缓冲区大小是性能和内存之间的权衡。默认值4096只是一个合理的选择，但与往常一样，先测量。
答案 3 :(得分：8)
Python本身可以在交互模式下为您提供帮助：
>>> help(file.read)
Help on method_descriptor:
read(...)
read([size]) -> read at most size bytes, returned as a string.
If the size argument is negative or omitted, read until EOF is reached.
Notice that when in non-blocking mode, less data than what was requested
may be returned, even if no size parameter was given.
答案 4 :(得分：5)
只需：
myfile = open(filename)
onecaracter = myfile.read(1)
答案 5 :(得分：4)
今天我在观看Raymond Hettinger的Transforming Code into Beautiful, Idiomatic Python时学到了一个新的习语：
import functools
with open(filename) as f:
f_read_ch = functools.partial(f.read, 1)
for ch in iter(f_read_ch, ''):
print 'Read a character:', repr(ch)
答案 6 :(得分：2)
你应该尝试f.read(1)，这绝对是正确的，也是正确的。
答案 7 :(得分：2)
只读一个字符
f.read(1)
答案 8 :(得分：0)
f = open('hi.txt', 'w')
f.write('0123456789abcdef')
f.close()
f = open('hej.txt', 'r')
f.seek(12)
print f.read(1) # This will read just "c"
答案 9 :(得分：0)
这也有效：
with open("filename") as fileObj:
for line in fileObj:
for ch in line:
print(ch)
它遍历文件中的每一行以及每行中的每个字符。
答案 10 :(得分：0)
要补充， 如果您正在读取包含vvvvery巨大的行的文件，这可能会破坏您的记忆，您可以考虑将它们读入缓冲区然后产生每个字符
def read_char(inputfile, buffersize=10240):
with open(inputfile, 'r') as f:
while True:
buf = f.read(buffersize)
if not buf:
break
for char in buf:
yield char
yield '' #handle the scene that the file is empty
if __name__ == "__main__":
for word in read_char('./very_large_file.txt'):
process(char)
答案 11 :(得分：0)
#reading out the file at once in a list and then printing one-by-one
f=open('file.txt')
for i in list(f.read()):
print(i)
答案 12 :(得分：0)
next答案 13 :(得分：0)
Python 3.8+ 的最佳答案：
with open(path, encoding="utf-8") as f:
while c := f.read(1):
do_my_thing(c)
您可能希望指定 utf-8 并避免使用平台编码。我选择在这里这样做。
函数 – Python 3.8+：
def stream_file_chars(path: str):
with open(path) as f:
while c := f.read(1):
yield c
函数 – Python<=3.7：
def stream_file_chars(path: str):
with open(path, encoding="utf-8") as f:
while True:
c = f.read(1)
if c == "":
break
yield c
功能 – 路径库 + 文档：
from pathlib import Path
from typing import Union, Generator
def stream_file_chars(path: Union[str, Path]) -> Generator[str, None, None]:
"""Streams characters from a file."""
with Path(path).open(encoding="utf-8") as f:
while (c := f.read(1)) != "":
yield c