QFile ¶

QFile class provides an interface for reading from and writing to files. 更多 …

继承者： QTemporaryFile

概要 ¶

函数 ¶

def copy (newName)
def exists ()
def link (newName)
def moveToTrash ()
def open (fd, ioFlags[, handleFlags=QFileDevice.DontCloseHandle])
def readLink ()
def remove ()
def rename (newName)
def setFileName (name)
def symLinkTarget ()

静态函数 ¶

def copy (fileName, newName)
def decodeName (localFileName)
def decodeName (localFileName)
def encodeName (fileName)
def exists (fileName)
def link (oldname, newName)
def moveToTrash (fileName[, pathInTrash=None])
def permissions (filename)
def readLink (fileName)
def remove (fileName)
def rename (oldName, newName)
def resize (filename, sz)
def setPermissions (filename, permissionSpec)
def symLinkTarget (fileName)

详细描述 ¶

QFile is an I/O device for reading and writing text and binary files and resources . A QFile may be used by itself or, more conveniently, with a QTextStream or QDataStream .

The file name is usually passed in the constructor, but it can be set at any time using setFileName() . QFile expects the file separator to be ‘/’ regardless of operating system. The use of other separators (e.g., ‘\’) is not supported.

You can check for a file’s existence using exists() , and remove a file using remove() . (More advanced file system related operations are provided by QFileInfo and QDir .)

The file is opened with open() , closed with close() , and flushed with flush() . Data is usually read and written using QDataStream or QTextStream , but you can also call the QIODevice -inherited functions read() , readLine() , readAll() , write() . QFile also inherits getChar() , putChar() ，和 ungetChar() , which work one character at a time.

The size of the file is returned by size() . You can get the current file position using pos() , or move to a new file position using seek() . If you’ve reached the end of the file, atEnd() 返回 true .

直接读取文件 ¶

The following example reads a text file line by line:
QFile file("in.txt");
if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
    return;
while (!file.atEnd()) {
    QByteArray line = file.readLine();
    process_line(line);
}
												
文本 flag passed to open() tells Qt to convert Windows-style line terminators (“\r\n”) into C++-style terminators (“\n”). By default, QFile assumes binary, i.e. it doesn’t perform any conversion on the bytes stored in the file.

使用流读取文件 ¶

The next example uses QTextStream to read a text file line by line:
QFile file("in.txt");
if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
    return;
QTextStream in(&file);
while (!in.atEnd()) {
    QString line = in.readLine();
    process_line(line);
}
												
QTextStream takes care of converting the 8-bit data stored on disk into a 16-bit Unicode QString . By default, it assumes that the user system’s local 8-bit encoding is used (e.g., UTF-8 on most unix based operating systems; see codecForLocale() for details). This can be changed using setCodec() .

To write text, we can use operator<<(), which is overloaded to take a QTextStream on the left and various data types (including QString ) on the right:
QFile file("out.txt");
if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
    return;
QTextStream out(&file);
out << "The magic number is: " << 49 << "\n";
												
QDataStream is similar, in that you can use operator<<() to write data and operator>>() to read it back. See the class documentation for details.

When you use QFile , QFileInfo ，和 QDir to access the file system with Qt, you can use Unicode file names. On Unix, these file names are converted to an 8-bit encoding. If you want to use standard C++ APIs ( <cstdio> or <iostream> ) or platform-specific APIs to access files instead of QFile , you can use the encodeName() and decodeName() functions to convert between Unicode file names and 8-bit file names.

On Unix, there are some special system files (e.g. in /proc ) for which size() will always return 0, yet you may still be able to read more data from such a file; the data is generated in direct response to you calling read() . In this case, however, you cannot use atEnd() to determine if there is more data to read (since atEnd() will return true for a file that claims to have size 0). Instead, you should either call readAll() , or call read() or readLine() repeatedly until no more data can be read. The next example uses QTextStream to read /proc/modules line by line:
QFile file("/proc/modules");
if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
    return;
QTextStream in(&file);
QString line = in.readLine();
while (!line.isNull()) {
    process_line(line);
    line = in.readLine();
}
												

信号 ¶

不像其它 QIODevice 实现，譬如 QTcpSocket , QFile does not emit the aboutToClose() , bytesWritten() ，或 readyRead() signals. This implementation detail means that QFile is not suitable for reading and writing certain types of files, such as device files on Unix platforms.

平台具体问题 ¶

文件权限的处理是不同的，在像 Unix 系统和 Windows。在非 writable directory on Unix-like systems, files cannot be created. This is not always the case on Windows, where, for instance, the ‘My Documents’ directory usually is not writable, but it is still possible to create files in it.

Qt’s understanding of file permissions is limited, which affects especially the setPermissions() function. On Windows, Qt will set only the legacy read-only flag, and that only when none of the Write* flags are passed. Qt does not manipulate access control lists (ACLs), which makes this function mostly useless for NTFS volumes. It may still be of use for USB sticks that use VFAT file systems. POSIX ACLs are not manipulated, either.

另请参阅

QTextStream QDataStream QFileInfo QDir Qt 资源系统

class QFile ¶

QFile(parent)

QFile(name)

QFile(name, parent)

param parent

QObject

param name

unicode

构造 QFile 对象。

构造新文件对象采用给定 parent .

static PySide2.QtCore.QFile. copy ( fileName , newName ) ¶

参数

fileName – unicode
newName – unicode

返回类型

bool

这是重载函数。

拷贝文件 fileName to newName 。返回 true 若成功；否则返回 false .

若文件采用名称 newName already exists, copy() 返回 false (即， QFile 不会覆写它)。

另请参阅

rename()

PySide2.QtCore.QFile. copy ( newName ) ¶

参数: newName – unicode
返回类型: bool

拷贝目前指定的文件通过 fileName() to a file called newName 。返回 true 若成功；否则返回 false .

注意：若文件采用名称 newName already exists, returns false (i.e. QFile 不会覆写它)。

关闭源文件在拷贝它之前。

另请参阅

setFileName()

static PySide2.QtCore.QFile. decodeName ( localFileName ) ¶

参数: localFileName – QByteArray
返回类型: unicode

static PySide2.QtCore.QFile. decodeName ( localFileName ) ¶

参数: localFileName – str
返回类型: unicode

这是重载函数。

返回 Unicode 版本为给定 localFileName 。见 encodeName() 了解细节。

static PySide2.QtCore.QFile. encodeName ( fileName ) ¶

参数: fileName – unicode
返回类型: QByteArray

转换 fileName to the local 8-bit encoding determined by the user’s locale. This is sufficient for file names that the user chooses. File names hard-coded into the application should only use 7-bit ASCII filename characters.

另请参阅

decodeName()

PySide2.QtCore.QFile. exists ( ) ¶

返回类型: bool

这是重载函数。

返回 true 若文件指定通过 fileName() 存在；否则返回 false .

另请参阅

fileName() setFileName()

static PySide2.QtCore.QFile. exists ( fileName ) ¶

参数: fileName – unicode
返回类型: bool

返回 true 若文件指定通过 fileName 存在；否则返回 false .

注意

若 fileName 是指向不存在文件的符号链接，返回 false。

PySide2.QtCore.QFile. link ( newName ) ¶

参数: newName – unicode
返回类型: bool

Creates a link named linkName that points to the file currently specified by fileName() . What a link is depends on the underlying filesystem (be it a shortcut on Windows or a symbolic link on Unix). Returns true 若成功；否则返回 false .

This function will not overwrite an already existing entity in the file system; in this case, link() will return false and set error() to return RenameError .

注意

To create a valid link on Windows, linkName must have a .lnk file extension.

另请参阅

setFileName()

static PySide2.QtCore.QFile. link ( oldname , newName ) ¶

参数

oldname – unicode
newName – unicode

返回类型

bool

这是重载函数。

Creates a link named linkName that points to the file fileName . What a link is depends on the underlying filesystem (be it a shortcut on Windows or a symbolic link on Unix). Returns true 若成功；否则返回 false .

另请参阅

link()

PySide2.QtCore.QFile. moveToTrash ( ) ¶

返回类型: bool

移动指定文件按 fileName() to the trash. Returns true 若成功，并设置 fileName() to the path at which the file can be found within the trash; otherwise returns false .

注意

On systems where the system API doesn’t report the location of the file in the trash, fileName() will be set to the null string once the file has been moved. On systems that don’t have a trash can, this function always returns false.

static PySide2.QtCore.QFile. moveToTrash ( fileName [ , pathInTrash=None ] ) ¶

参数

fileName – unicode
pathInTrash – unicode

返回类型

bool

这是重载函数。

移动指定文件按 fileName() to the trash. Returns true if successful, and sets pathInTrash (if provided) to the path at which the file can be found within the trash; otherwise returns false .

注意

On systems where the system API doesn’t report the path of the file in the trash, pathInTrash will be set to the null string once the file has been moved. On systems that don’t have a trash can, this function always returns false.

PySide2.QtCore.QFile. open ( fd , ioFlags [ , handleFlags=QFileDevice.DontCloseHandle ] ) ¶

参数

fd – int
ioFlags – OpenMode
handleFlags – FileHandleFlags

返回类型

bool

这是重载函数。

Opens the existing file descriptor fd 以给定 mode . handleFlags may be used to specify additional options. Returns true 若成功；否则返回 false .

当 QFile is opened using this function, behaviour of close() is controlled by the AutoCloseHandle flag. If AutoCloseHandle is specified, and this function succeeds, then calling close() closes the adopted handle. Otherwise, close() does not actually close the file, but only flushes it.

QFile that is opened using this function is automatically set to be in raw mode; this means that the file input/output functions are slow. If you run into performance issues, you should try to use one of the other open functions.

警告

若 fd is not a regular file, e.g, it is 0 ( stdin ), 1 ( stdout ), or 2 ( stderr ), you may not be able to seek() . In those cases, size() 返回 0 。见 isSequential() 了解更多信息。

警告

Since this function opens the file without specifying the file name, you cannot use this QFile 采用 QFileInfo .

另请参阅

close()

static PySide2.QtCore.QFile. permissions ( filename ) ¶

参数: filename – unicode
返回类型: Permissions

这是重载函数。

Returns the complete OR-ed together combination of Permission for fileName .

PySide2.QtCore.QFile. readLink ( ) ¶

返回类型: unicode

注意

此函数被弃用。

使用 symLinkTarget() 代替。

static PySide2.QtCore.QFile. readLink ( fileName ) ¶

参数: fileName – unicode
返回类型: unicode

注意

此函数被弃用。

使用 symLinkTarget() 代替。

PySide2.QtCore.QFile. remove ( ) ¶

返回类型: bool

Removes the file specified by fileName() 。返回 true 若成功；否则返回 false .

The file is closed before it is removed.

另请参阅

setFileName()

static PySide2.QtCore.QFile. remove ( fileName ) ¶

参数: fileName – unicode
返回类型: bool

这是重载函数。

Removes the file specified by the fileName 给定。

返回 true 若成功；否则返回 false .

另请参阅

remove()

PySide2.QtCore.QFile. rename ( newName ) ¶

参数: newName – unicode
返回类型: bool

Renames the file currently specified by fileName() to newName 。返回 true 若成功；否则返回 false .

若文件采用名称 newName already exists, returns false (即， QFile 不会覆写它)。

The file is closed before it is renamed.

If the rename operation fails, Qt will attempt to copy this file’s contents to newName , and then remove this file, keeping only newName . If that copy operation fails or this file can’t be removed, the destination file newName is removed to restore the old state.

另请参阅

setFileName()

static PySide2.QtCore.QFile. rename ( oldName , newName ) ¶

参数

oldName – unicode
newName – unicode

返回类型

bool

这是重载函数。

Renames the file oldName to newName 。返回 true 若成功；否则返回 false .

若文件采用名称 newName already exists, rename() 返回 false (即， QFile 不会覆写它)。

另请参阅

rename()

static PySide2.QtCore.QFile. resize ( filename , sz ) ¶

参数

filename – unicode
sz – qint64

返回类型

bool

这是重载函数。

集 fileName to size (in bytes) sz 。返回 true if the resize succeeds; false otherwise. If sz is larger than fileName currently is the new bytes will be set to 0, if sz is smaller the file is simply truncated.

警告

This function can fail if the file doesn’t exist.

另请参阅

resize()

PySide2.QtCore.QFile. setFileName ( name ) ¶

参数: name – unicode

设置 name of the file. The name can have no path, a relative path, or an absolute path.

Do not call this function if the file has already been opened.

If the file name has no path or a relative path, the path used will be the application’s current directory path at the time of the open() ** call.

范例：

												file = QFile()
QDir.setCurrent("/tmp")
file.setFileName("readme.txt")
QDir.setCurrent("/home")
file.open(QIODevice.ReadOnly)       # opens "/home/readme.txt" under Unix
												
											

Note that the directory separator “/” works for all operating systems supported by Qt.

另请参阅

fileName() QFileInfo QDir

static PySide2.QtCore.QFile. setPermissions ( filename , permissionSpec ) ¶

参数

filename – unicode
permissionSpec – Permissions

返回类型

bool

这是重载函数。

设置权限为 fileName file to permissions .

PySide2.QtCore.QFile. symLinkTarget ( ) ¶

返回类型: unicode

这是重载函数。

Returns the absolute path of the file or directory a symlink (or shortcut on Windows) points to, or a an empty string if the object isn’t a symbolic link.

This name may not represent an existing file; it is only a string. exists() 返回 true if the symlink points to an existing file.

另请参阅

fileName() setFileName()

static PySide2.QtCore.QFile. symLinkTarget ( fileName ) ¶

参数: fileName – unicode
返回类型: unicode

Returns the absolute path of the file or directory referred to by the symlink (or shortcut on Windows) specified by fileName , or returns an empty string if the fileName does not correspond to a symbolic link.

This name may not represent an existing file; it is only a string. exists() 返回 true if the symlink points to an existing file.

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QFile ¶

概要 ¶

函数 ¶

静态函数 ¶

详细描述 ¶

直接读取文件 ¶

使用流读取文件 ¶

信号 ¶

平台具体问题 ¶