Python StringIO用法及代碼示例

StringIO 模塊是一個內存中的類似文件的對象。該對象可用作大多數需要標準文件對象的函數的輸入或輸出。創建 StringIO 對象時，通過將字符串傳遞給構造函數來對其進行初始化。如果沒有傳遞任何字符串，StringIO 將以空開始。在這兩種情況下，文件上的初始光標都從零開始。

注意：最新版本的 Python 中不存在此模塊，因此要使用此模塊，我們必須從 Python 中的 io 模塊將其導入為 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())

輸出：

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():該函數返回文件的全部內容。

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())

輸出：

'Hello and welcome to GeeksForGeeks.'

2. 在本文中，我們討論 StringIO 的一些返回布爾值的函數，即 True 或 false：

StringIO.isatty():如果流是交互式的，則此函數返回 True；如果流不是交互式的，則返回 False
StringIO.readable():如果文件可讀，則該函數返回 True；如果文件不可讀，則返回 False。
StringIO.writable():如果文件支持寫入，則該函數返回 True；如果文件不支持寫入，則返回 False。
StringIO.seekable():如果文件支持隨機訪問，則此函數返回 True；如果文件不支持隨機訪問，則返回 False。
StringIO.關閉：如果文件關閉則此函數返回 True，如果文件打開則返回 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)

輸出：

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()函數用於設置光標在文件上的位置。如果我們對文件執行任何讀寫操作，光標將設置在最後一個索引上，以便將光標移動到文件的起始索引處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())

輸出：

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

4.StringIO.truncate()：該函數用於調整文件流的大小。此方法在提供的索引之後刪除文件並保存它。

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())

輸出：

Hello and welcome to GeeksForGeeks.
Hello and welcome

5.StringIO.tell()：該方法用於告知文件的當前流或光標位置。

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())

輸出：

0
20

6.StringIO.close()：該方法用於關閉文件。在文件上調用此函數後，我們無法對該文件執行任何操作。如果執行任何操作，都會引發 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)

輸出：

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

相關用法

注：本文由純淨天空篩選整理自VishwashVishwakarma大神的英文原創作品 StringIO Module in Python。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。