Creating an FTP client with Python

Question

I've always thought about creating my own ftp client ever since I've started using the Internet. And now that I'm studying Python, I'm thinking about creating one as an exercises/personal project.

I'm wondering,

• What libraries do you guys suggest? Will ftplib suffice? Or would you suggest another library(preferably one that has good docs)?
• I'm thinking about using wxPython. Is it a good idea? Should I learn it first?
• I'm coming from a Web Development background. What tips/suggestions would you guys give to me?

I'd appreciate any guidance/help. Thanks in advance! :)

Answer 1

It sounds like you want to make a program that has a GUI. May I recommend using PyQt for that part of your application? ftplib should be fine for your FTP support, and you can find documentation right here .

Alternatively for FTP support, you can use the QFtp class from the QtNetwork module from PyQt framework. The following is an example FTP client that comes with PyQt. The images come with it.

#!/usr/bin/env python

"""PyQt4 port of the network/ftp example from Qt v4.x"""

# This is only needed for Python v2 but is harmless for Python v3.
import sip
sip.setapi('QString', 2)

from PyQt4 import QtCore, QtGui, QtNetwork

import ftp_rc


class FtpWindow(QtGui.QDialog):
    def __init__(self, parent=None):
        super(FtpWindow, self).__init__(parent)

        self.isDirectory = {}
        self.currentPath = ''
        self.ftp = None
        self.outFile = None

        ftpServerLabel = QtGui.QLabel("Ftp &server:")
        self.ftpServerLineEdit = QtGui.QLineEdit('ftp.trolltech.com')
        ftpServerLabel.setBuddy(self.ftpServerLineEdit)

        self.statusLabel = QtGui.QLabel("Please enter the name of an FTP server.")

        self.fileList = QtGui.QTreeWidget()
        self.fileList.setEnabled(False)
        self.fileList.setRootIsDecorated(False)
        self.fileList.setHeaderLabels(("Name", "Size", "Owner", "Group", "Time"))
        self.fileList.header().setStretchLastSection(False)

        self.connectButton = QtGui.QPushButton("Connect")
        self.connectButton.setDefault(True)

        self.cdToParentButton = QtGui.QPushButton()
        self.cdToParentButton.setIcon(QtGui.QIcon(':/images/cdtoparent.png'))
        self.cdToParentButton.setEnabled(False)

        self.downloadButton = QtGui.QPushButton("Download")
        self.downloadButton.setEnabled(False)

        self.quitButton = QtGui.QPushButton("Quit")

        buttonBox = QtGui.QDialogButtonBox()
        buttonBox.addButton(self.downloadButton,
                QtGui.QDialogButtonBox.ActionRole)
        buttonBox.addButton(self.quitButton, QtGui.QDialogButtonBox.RejectRole)

        self.progressDialog = QtGui.QProgressDialog(self)

        self.fileList.itemActivated.connect(self.processItem)
        self.fileList.currentItemChanged.connect(self.enableDownloadButton)
        self.progressDialog.canceled.connect(self.cancelDownload)
        self.connectButton.clicked.connect(self.connectOrDisconnect)
        self.cdToParentButton.clicked.connect(self.cdToParent)
        self.downloadButton.clicked.connect(self.downloadFile)
        self.quitButton.clicked.connect(self.close)

        topLayout = QtGui.QHBoxLayout()
        topLayout.addWidget(ftpServerLabel)
        topLayout.addWidget(self.ftpServerLineEdit)
        topLayout.addWidget(self.cdToParentButton)
        topLayout.addWidget(self.connectButton)

        mainLayout = QtGui.QVBoxLayout()
        mainLayout.addLayout(topLayout)
        mainLayout.addWidget(self.fileList)
        mainLayout.addWidget(self.statusLabel)
        mainLayout.addWidget(buttonBox)
        self.setLayout(mainLayout)

        self.setWindowTitle("FTP")

    def sizeHint(self):
        return QtCore.QSize(500, 300)

    def connectOrDisconnect(self):
        if self.ftp:
            self.ftp.abort()
            self.ftp.deleteLater()
            self.ftp = None

            self.fileList.setEnabled(False)
            self.cdToParentButton.setEnabled(False)
            self.downloadButton.setEnabled(False)
            self.connectButton.setEnabled(True)
            self.connectButton.setText("Connect")
            self.setCursor(QtCore.Qt.ArrowCursor)

            return

        self.setCursor(QtCore.Qt.WaitCursor)

        self.ftp = QtNetwork.QFtp(self)
        self.ftp.commandFinished.connect(self.ftpCommandFinished)
        self.ftp.listInfo.connect(self.addToList)
        self.ftp.dataTransferProgress.connect(self.updateDataTransferProgress)

        self.fileList.clear()
        self.currentPath = ''
        self.isDirectory.clear()

        url = QtCore.QUrl(self.ftpServerLineEdit.text())
        if not url.isValid() or url.scheme().lower() != 'ftp':
            self.ftp.connectToHost(self.ftpServerLineEdit.text(), 21)
            self.ftp.login()
        else:
            self.ftp.connectToHost(url.host(), url.port(21))

            user_name = url.userName()
            if user_name:
                try:
                    # Python v3.
                    user_name = bytes(user_name, encoding='latin1')
                except:
                    # Python v2.
                    pass

                self.ftp.login(QtCore.QUrl.fromPercentEncoding(user_name), url.password())
            else:
                self.ftp.login()

            if url.path():
                self.ftp.cd(url.path())

        self.fileList.setEnabled(True)
        self.connectButton.setEnabled(False)
        self.connectButton.setText("Disconnect")
        self.statusLabel.setText("Connecting to FTP server %s..." % self.ftpServerLineEdit.text())

    def downloadFile(self):
        fileName = self.fileList.currentItem().text(0)

        if QtCore.QFile.exists(fileName):
            QtGui.QMessageBox.information(self, "FTP",
                    "There already exists a file called %s in the current "
                    "directory." % fileName)
            return

        self.outFile = QtCore.QFile(fileName)
        if not self.outFile.open(QtCore.QIODevice.WriteOnly):
            QtGui.QMessageBox.information(self, "FTP",
                    "Unable to save the file %s: %s." % (fileName, self.outFile.errorString()))
            self.outFile = None
            return

        self.ftp.get(self.fileList.currentItem().text(0), self.outFile)

        self.progressDialog.setLabelText("Downloading %s..." % fileName)
        self.downloadButton.setEnabled(False)
        self.progressDialog.exec_()

    def cancelDownload(self):
        self.ftp.abort()

    def ftpCommandFinished(self, _, error):
        self.setCursor(QtCore.Qt.ArrowCursor)

        if self.ftp.currentCommand() == QtNetwork.QFtp.ConnectToHost:
            if error:
                QtGui.QMessageBox.information(self, "FTP",
                        "Unable to connect to the FTP server at %s. Please "
                        "check that the host name is correct." % self.ftpServerLineEdit.text())
                self.connectOrDisconnect()
                return

            self.statusLabel.setText("Logged onto %s." % self.ftpServerLineEdit.text())
            self.fileList.setFocus()
            self.downloadButton.setDefault(True)
            self.connectButton.setEnabled(True)
            return

        if self.ftp.currentCommand() == QtNetwork.QFtp.Login:
            self.ftp.list()

        if self.ftp.currentCommand() == QtNetwork.QFtp.Get:
            if error:
                self.statusLabel.setText("Canceled download of %s." % self.outFile.fileName())
                self.outFile.close()
                self.outFile.remove()
            else:
                self.statusLabel.setText("Downloaded %s to current directory." % self.outFile.fileName())
                self.outFile.close()

            self.outFile = None
            self.enableDownloadButton()
            self.progressDialog.hide()
        elif self.ftp.currentCommand() == QtNetwork.QFtp.List:
            if not self.isDirectory:
                self.fileList.addTopLevelItem(QtGui.QTreeWidgetItem(["<empty>"]))
                self.fileList.setEnabled(False)

    def addToList(self, urlInfo):
        item = QtGui.QTreeWidgetItem()
        item.setText(0, urlInfo.name())
        item.setText(1, str(urlInfo.size()))
        item.setText(2, urlInfo.owner())
        item.setText(3, urlInfo.group())
        item.setText(4, urlInfo.lastModified().toString('MMM dd yyyy'))

        if urlInfo.isDir():
            icon = QtGui.QIcon(':/images/dir.png')
        else:
            icon = QtGui.QIcon(':/images/file.png')
        item.setIcon(0, icon)

        self.isDirectory[urlInfo.name()] = urlInfo.isDir()
        self.fileList.addTopLevelItem(item)
        if not self.fileList.currentItem():
            self.fileList.setCurrentItem(self.fileList.topLevelItem(0))
            self.fileList.setEnabled(True)

    def processItem(self, item):
        name = item.text(0)
        if self.isDirectory.get(name):
            self.fileList.clear()
            self.isDirectory.clear()
            self.currentPath += '/' + name
            self.ftp.cd(name)
            self.ftp.list()
            self.cdToParentButton.setEnabled(True)
            self.setCursor(QtCore.Qt.WaitCursor)

    def cdToParent(self):
        self.setCursor(QtCore.Qt.WaitCursor)
        self.fileList.clear()
        self.isDirectory.clear()

        dirs = self.currentPath.split('/')
        if len(dirs) > 1:
            self.currentPath = ''
            self.cdToParentButton.setEnabled(False)
            self.ftp.cd('/')
        else:
            self.currentPath = '/'.join(dirs[:-1])
            self.ftp.cd(self.currentPath)

        self.ftp.list()

    def updateDataTransferProgress(self, readBytes, totalBytes):
        self.progressDialog.setMaximum(totalBytes)
        self.progressDialog.setValue(readBytes)

    def enableDownloadButton(self):
        current = self.fileList.currentItem()
        if current:
            currentFile = current.text(0)
            self.downloadButton.setEnabled(not self.isDirectory.get(currentFile))
        else:
            self.downloadButton.setEnabled(False)


if __name__ == '__main__':

    import sys

    app = QtGui.QApplication(sys.argv)
    ftpWin = FtpWindow()
    ftpWin.show()
    sys.exit(ftpWin.exec_())

Answer 2

Python's standard library is just a great place to start: http://docs.python.org/library/ftplib.html

Note: And if for some reason you want to write your own client, you can simple read the source, which is a good training exercise in itself ...