Python StringIO用法及代码示例

StringIO 模块是一个内存中的类似文件的对象。该对象可用作大多数需要标准文件对象的函数的输入或输出。创建 StringIO 对象时，通过将字符串传递给构造函数来对其进行初始化。如果没有传递任何字符串，StringIO 将以空开始。在这两种情况下，文件上的初始光标都从零开始。

注意：最新版本的 Python 中不存在此模块，因此要使用此模块，我们必须从 Python 中的 io 模块将其导入为 io.StringIO。

例子：

Python3


# Importing the StringIO module.
from io import StringIO  
# The arbitrary string.
string ='This is initial string.'
# Using the StringIO method to set
# as file object. Now we have an 
# object file that we will able to
# treat just like a file.
file = StringIO(string)
# this will read the file 
print(file.read())
# We can also write this file.
file.write(" Welcome to geeksforgeeks.")
# This will make the cursor at 
# index 0.
file.seek(0)
# This will print the file after 
# writing in the initial string.
print('The string after writing is:', file.read())

输出：

This is initial string.
The string after writing is: This is initial string. Welcome to geeksforgeeks.

StringIO的一些重要方法如下：

1. StringIO.getvalue():该函数返回文件的全部内容。

用法:

File_name.getvalue()

例子：

Python3


# Importing the StringIO module.
from io import StringIO  
# The arbitrary string.
string ='Hello and welcome to GeeksForGeeks.'
# Using the StringIO method to 
# set as file object.
file = StringIO(string) 
# Retrieve the entire content of the file.
print(file.getvalue())

输出：

'Hello and welcome to GeeksForGeeks.'

2. 在本文中，我们讨论 StringIO 的一些返回布尔值的函数，即 True 或 false：

StringIO.isatty():如果流是交互式的，则此函数返回 True；如果流不是交互式的，则返回 False
StringIO.readable():如果文件可读，则该函数返回 True；如果文件不可读，则返回 False。
StringIO.writable():如果文件支持写入，则该函数返回 True；如果文件不支持写入，则返回 False。
StringIO.seekable():如果文件支持随机访问，则此函数返回 True；如果文件不支持随机访问，则返回 False。
StringIO.关闭：如果文件关闭则此函数返回 True，如果文件打开则返回 False。

用法:

File_name.isatty()
File_name.readable()
File_name.writable()
File_name.seekable()
File_name.closed

例子：

Python3


# Importing the StringIO module.
from io import StringIO  
# The arbitrary string.
string ='Hello and welcome to GeeksForGeeks.'
# Using the StringIO method to 
# set as file object.
file = StringIO(string) 
# This will returns whether the file
# is interactive or not.
print("Is the file stream interactive?", file.isatty()) 
# This will returns whether the file is
# readable or not.
print("Is the file stream readable?", file.readable())
# This will returns whether the file supports 
# writing or not.
print("Is the file stream writable?", file.writable())
# This will returns whether the file is
# seekable or not.
print("Is the file stream seekable?", file.seekable())
# This will returns whether the file is 
# closed or not.
print("Is the file closed?", file.closed)

输出：

Is the file stream interactive? False
Is the file stream readable? True
Is the file stream writable? True
Is the file stream seekable? True
Is the file closed? False

3.StringIO.seek()：seek()函数用于设置光标在文件上的位置。如果我们对文件执行任何读写操作，光标将设置在最后一个索引上，以便将光标移动到文件的起始索引处seek()。

用法:

File_name.seek(argument) 
# Here the argument is passed to tell the 
# function  where to set the cursor position.

例子：

Python3


# Importing the StringIO module.
from io import StringIO  
# The arbitrary string.
string ='Hello and welcome to GeeksForGeeks.'
# Using the StringIO method 
# to set as file object.
file = StringIO(string) 
# Reading the file:
print(file.read())
# Now if we again want to read
# the file it shows empty file
# because the cursor is set to 
# the last index.
# This does not print anything
# because the function returns an
# empty string.
print(file.read()) 
# Hence to set the cursor position
# to read or write the file again
# we use seek().We can pass any index
# here from(0 to len(file))
file.seek(0) 
# Now we can able to read the file again()
print(file.read())

输出：

Hello and welcome to GeeksForGeeks.
Hello and welcome to GeeksForGeeks.

4.StringIO.truncate()：该函数用于调整文件流的大小。此方法在提供的索引之后删除文件并保存它。

用法:

File_name.truncate(size = None)
# We can provide the size from where 
# to truncate the file.

例子：

Python3


# Importing the StringIO module.
from io import StringIO  
# The arbitrary string.
string ='Hello and welcome to GeeksForGeeks.'
# Using the StringIO method
# to set as file object.
file = StringIO(string) 
# Reading the initial file:
print(file.read())
# To set the cursor at 0.
file.seek(0) 
# This will drop the file after 
# index 18.
file.truncate(18)
# File after truncate.
print(file.read())

输出：

Hello and welcome to GeeksForGeeks.
Hello and welcome

5.StringIO.tell()：该方法用于告知文件的当前流或光标位置。

用法:

File_name.tell()

例子：

Python3


# Importing the StringIO module.
from io import StringIO  
# The arbitrary string.
string ='Hello and welcome to GeeksForGeeks.'
# Using the StringIO method to 
# set as file object.
file = StringIO(string)
# Here the cursor is at index 0.
print(file.tell())
# Cursor is set to index 20.
file.seek(20)
# Print the index of cursor
print(file.tell())

输出：

0
20

6.StringIO.close()：该方法用于关闭文件。在文件上调用此函数后，我们无法对该文件执行任何操作。如果执行任何操作，都会引发 ValueError。

用法:

File_name.close()

例子：

Python3


# Importing the StringIO module.
from io import StringIO  
# The arbitrary string.
string ='Hello and welcome to GeeksForGeeks.'
# Using the StringIO method to
# set as file object.
file = StringIO(string)
# Reading the file.
print(file.read()) 
# Closing the file.
file.close() 
# If we now perform any operation on the file 
# it will raise an ValueError.
# This is to know whether the
# file is closed or not.
print("Is the file closed?", file.closed)

输出：

Hello and welcome to GeeksForGeeks.
Is the file closed? True

相关用法

注：本文由纯净天空筛选整理自VishwashVishwakarma大神的英文原创作品 StringIO Module in Python。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。