Python의 파일에서 한 번에 한 문자를 읽는 방법은 무엇입니까?

Python의 파일에서 한 번에 한 문자를 읽는 방법은 무엇입니까?

---

누구든지 내가 어떻게 할 수 있는지 말해 줄 수 있습니까?

---

with open(filename) as f:
  while True:
    c = f.read(1)
    if not c:
      print "End of file"
      break
    print "Read a character:", c

---

먼저 파일을 엽니 다.

with open("filename") as fileobj:
    for line in fileobj:  
       for ch in line: 
           print ch

---

나는 받아 들여진 대답을 좋아한다 : 그것은 간단하고 일을 끝낼 것이다. 또한 대체 구현을 제공하고 싶습니다.

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))

내가 제안하는 코드는 기본적으로 허용되는 답변과 동일한 아이디어입니다. 파일에서 주어진 바이트 수를 읽습니다. 차이점은 먼저 좋은 데이터 청크를 읽은 다음 (4006은 X86의 좋은 기본값이지만 1024 또는 8192, 페이지 크기의 배수를 시도 할 수 있음) 해당 청크의 문자를 산출한다는 것입니다. 하나씩.

내가 제시하는 코드는 더 큰 파일의 경우 더 빠를 수 있습니다. 예를 들어 톨스토이가 쓴 전쟁과 평화의 전체 텍스트를 보자 . 다음은 내 타이밍 결과입니다 (OS X 10.7.4를 사용하는 Mac Book Pro; so.py는 내가 붙여 넣은 코드에 지정한 이름입니다).

$ 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

Now: do not take the buffer size at 4096 as a universal truth; look at the results I get for different sizes (buffer size (bytes) vs wall time (sec)):

   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 

As you can see, you can start seeing gains earlier on (and my timings are likely very inaccurate); the buffer size is a trade-off between performance and memory. The default of 4096 is just a reasonable choice but, as always, measure first.

---

Python itself can help you with this, in interactive mode:

>>> 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.

---

Just:

myfile = open(filename)
onecaracter = myfile.read(1)

---

I learned a new idiom for this today while watching Raymond Hettinger's Transforming Code into Beautiful, Idiomatic Python:

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) 

---

Just read a single character

f.read(1)

---

You should try f.read(1), which is definitely correct and the right thing to do.

---

This will also work:

with open("filename") as fileObj:
    for line in fileObj:  
        for ch in line:
            print(ch)

It goes through every line in the the file and every character in every line.

---

#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)

---

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"

---

To make a supplement, if you are reading file that contains a line that is vvvvery huge, which might break your memory, you might consider read them into a buffer then yield the each char

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)

참고URL : https://stackoverflow.com/questions/2988211/how-to-read-a-single-character-at-a-time-from-a-file-in-python