Question

app = Flask(__name__)
@app.route("/")
def hello():
    address="someserver"
    global FTP
    ftp = FTP(address)
    ftp.login()
    return ftp.retrlines("LIST")

if __name__ == "__main__":
    app.run()

...这给了我以下输出：

226-Options: -l 226 1 matches total

问题是 - 为什么不打印后退的输出，我该怎么做？

Answer 1

ftplib.FTP类的文档说retrlines采用可选回调 - 如果没有提供回调“默认回调将该行打印到sys.stdout。”这意味着方法retrlines实际上不返回提供的数据 - 它只是在接收到每个行时将其传递给可传递给它的可调用对象。这为您提供了几个选项：

传入一个可以存储多次被调用结果的可调用对象：

def fetchlines(line=None):
    if line is not None:
        # As long as we are called with a line
        # store the line in the array we added to this function
        fetchlines.lines.append(line)
    else:
        # When we are called without a line
        # we are retrieving the lines
        # Truncate the array after copying it
        # so we can re-use this function
        lines = fetchlines.lines[:]
        fetchlines.lines = []
        return lines

fetchlines.lines = []

@app.route("/")
def hello():
    ftp = FTP("someaddress")
    ftp.login()
    ftp.dir(fetchlines)
    lines = fetchlines()
    return "<br>".join(lines)

将sys.stdout替换为类似文件的对象（例如，来自cStringIO）然后只需读取该文件：

from cStringIO import StringIO
from sys import stdout

# Save a reference to stdout
STANDARD_OUT = stdout

@app.route("/")
def hello():
    ftp = FTP("someaddress")
    ftp.login()

    # Change stdout to point to a file-like object rather than a terminal
    file_like = StringIO()
    stdout = file_like

    ftp.dir()

    # lines in this case will be a string, not a list
    lines = file_like.getvalue()

    stdout = STANDARD_OUT
    file_like.close()

    return lines

这些技术都不会在很多负载下保持良好状态 - 甚至在任何真正的并发下都不会。有办法解决这个问题，但我会留下另一天。

flask + ftplib基本应用程序

1 个答案: