Python seek()方法

Python seek()方法用於更改文件句柄的當前位置。文件句柄就像一個游標，用於定義必須在文件中讀取或寫入的數據的位置。

語法:

fi.seek(offset, from_where), where fi is the file pointer

參數:

偏移量:用於定義向前移動的位置數。

from_where: 用於定義參考點。

注意:Python 中的 seek()方法不返回值。

from_where 參數用於選擇參考點。它可以接受三個值:

• 0:0 值用於設置文件開頭的 what 參數。
• 1:1 值用於在文件的當前位置設置 whence 參數。
• 2:2 值用於設置文件末尾的 what 參數。

默認情況下，from_where 參數設置為 0。因此，在文本模式下，參考點不能設置為當前位置或結束位置，除非偏移量等於 0。

示例 1: (用戶必須讀取包含以下文本的文本文件:

「這是我寫的句子，展示了在 Python 中使用 seek()方法的例子。」

fi = open("text.txt", "r")
# the second parameter of the seek method is by default 0
fi.seek(30)
# now, we will print the current position
print(fi.tell())

print(fi.readline())
fi.close()

輸出:

30
ing to show the example of the seek() method working in Python.

示例文本文件-

# let's assuming the text file has following 5 lines
# line 1: This is the sentence I am Writing to show the example of the seek() 
# method working in Python.
# line 2: The line no. 2 for showing the second method of writing the seek() 
# method is python
# Line 3: the line no. 3 for showing the second method 
# Line 4: the line no. 4 for showing the second method 
# Line 5: the line no. 5 for showing the second method 

例 2:(方法 2)

fi = open ("text.txt", "r+")
print ("Name of the file: ", fi.name)

line_1 = fi.readline()
print ("Read Line: %s" % (line_1))

# Again, set the pointer to the beginning
fi.seek (0, 1)
line_2 = fi.readline()
print ("Read Line: %s" % (line_2))

# Close opend file
fi.close()

輸出:

Name of the file:  text.txt
Read Line: This is the sentence I am Writing to show the example of the seek() method working in Python.

Read Line: The line no. 2 for showing the second method of writing the seek() method is python

seek()方法也可以使用負偏移量，但只能在文件以二進位模式打開時使用。

例 3:(負偏移)

fi = open ("text.txt", "rb")

# the user is setting the reference point to thirtieth position to the left from 
# end
fi.seek (-70, 2)

# now print the current position
print (fi.tell())

# now the user will Convert the binary to string 
print (fi.readline().decode('utf-8'))

fi.close()

輸出:

25
 Writing to show the example of the seek() method working in Python.