![\"A](\"https:\/\/www.jquery-az.com\/wp-content\/uploads\/2017\/12\/Python-open-function.jpg\")
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What is Python open() function?<\/strong><\/p>\n In order to perform input\/output (I\/O) operations in files, you have to open a file.<\/p>\n The Python open() function is used to open the specified file where you may perform reading, writing, and other operations.<\/p>\n In this tutorial, I will show you how to open a file, read the content of a file, write to a file, and do other related things.<\/p>\n<\/div>\n The syntax of using the open() function is:<\/p>\n The parameters of the open function are explained below:<\/p>\n In this example, a text file is opened in read-only mode by using the \u2018r\u2019<\/strong> value for the mode parameter in Python open() file function.<\/p>\n The text of the readme.txt<\/em> file is displayed on the screen.<\/p>\n The readme.txt file is placed at the same location where the Python source file is placed:<\/p>\n The following things should be noted in the program:<\/strong><\/p>\n The following example shows using the Python write() method after creating a file object.<\/p>\n In the open() function, the \u2018w<\/strong>\u2019 parameter is given for the mode<\/strong> argument.<\/p>\n This enables us to write in a text file, however, the text file will be truncated while using this value. That means the existing text will be removed.<\/p>\n To demonstrate that, the content in the \u201creadme.txt\u201d file initially is \u201cHello World Python\u201d. This is displayed before opening the file in read-only mode.<\/p>\n After that, the file is opened again in write-only<\/strong> mode, and the write() <\/strong>method is used for adding new text.<\/p>\n The file is closed again and reopened in read-only mode for displaying the content:<\/p>\n You can see, the initial text is truncated as we opened the file in write-only mode. The second print function displays only the newly written text.<\/p>\n If you require keeping the initial text and avoid truncating this while writing to file then you may use the file append mode<\/strong>.<\/p>\n For that, use the \u2018a\u2019 <\/strong>value for the mode parameter. This will append the new text to the end of existing content.<\/p>\n See this example where a few changes are made in the above example. The file text before and after writing the new text is displayed and you can see the difference.<\/p>\n The new content is added ahead of the existing text. The newline \u2018\\n<\/strong>\u2019 is used for writing text in the next line.<\/p>\n In all the above examples, the complete content of the text file is read and displayed by using the open() function\u2019s read() method. If you require only a part of the\u00a0text from the file then you may specify the size<\/strong> in the read() method as follows:<\/p>\n The output:<\/strong><\/p>\n Reading limited data:\u00a0 Python Hel<\/p>\n >>><\/p>\n<\/div>\n By default, the entire content is read and returned (if size is left as in the above examples).<\/p>\n Also, note that\u00a0the returned data is either string<\/strong> for the text files and bytes object<\/strong> for binary mode.<\/p>\n You may use a for loop to loop over a file object for reading line by line. Have a look at this example where I wrote a few lines of text in the readme.txt file:<\/p>\n The output:<\/strong><\/p>\n Line 1- Python is cool<\/p>\n Line 2- Python is Great<\/p>\n Line 3- Python is Awesome<\/p>\n Line 4- Love it!!!<\/p>\n<\/div>\n This way of reading line by line is memory efficient and fast.<\/p>\n The readline() method<\/strong> can also be used for reading a single line from the file. In that case, the new line character is left at the end of the string. The new line is omitted at the last line.<\/p>\nHow to open files in Python?<\/strong><\/h3>\n
open(file, mode=’r’, buffering=-1, encoding=None, errors=None, newline=None)<\/div>\n\n\n
\n \nParameter<\/th>\n Description<\/th>\n<\/tr>\n<\/thead>\n \n file<\/code><\/td>\nSpecifies the relative or absolute path to the file you want to open. An error (OSError) occurs if the file cannot be opened.<\/td>\n<\/tr>\n \n mode<\/code><\/td>\nSpecifies the purpose of opening the file, such as ‘r’ for reading, ‘w’ for writing, and ‘a’ for appending. Detailed mode options are provided in the last section.<\/td>\n<\/tr>\n \n buffering<\/code><\/td>\nSets buffering on or off, using an Integer value. 1 enables text-mode line buffering, and 0 disables buffering in binary mode. This parameter is optional. The default buffering policy is applied if not provided.<\/td>\n<\/tr>\n \n newline<\/code><\/td>\nApplies to text-mode only and specifies universal newlines. Valid values include ‘\\n’, ‘\\r’, ‘\\r\\n’, None, and ”.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n An example of reading a file by read method of open() function<\/strong><\/h3>\n
# The example of open() functio for reading a text file\r\n\r\nobjFile = open(\"readme.txt\", \"r\")\r\n\r\nfileContent = objFile.read();\r\n\r\nprint (\"The text file contains: : \", fileContent)\r\n\r\n\r\n# After performing the operation, close the file\r\n\r\nobjFile.close()<\/pre>\n
![\"Python](\"https:\/\/www.jquery-az.com\/wp-content\/uploads\/2017\/11\/61.1-Python-open.png\")
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The example of write to file by write() method<\/strong><\/h3>\n
# The example of open() functio for reading a text file\r\n\r\n\r\nobjRead1 = open(\"readme.txt\", \"r\")\r\n\r\nContFile = objRead1.read();\r\n\r\nprint (\"Content before write() : \", ContFile)\r\n\r\n# Closing the first instance\r\n\r\nobjRead1.close()\r\n\r\n\r\n#Opening again for write to file\r\n\r\nobjWrite = open(\"readme.txt\", \"w\")\r\n\r\nobjWrite.write (\"Using 'w' for writing text in file\")\r\n\r\n\r\n#Closing the file in write mode\r\n\r\nobjWrite.close()\r\n\r\n\r\n#Openging the file again for displaying content after writing\r\n\r\nobjRead2 = open(\"readme.txt\", \"r\")\r\n\r\nContAfterWrite = objRead2.read();\r\n\r\nprint (\"The content after write() : \", ContAfterWrite)\r\n\r\n\r\nobjRead2.close()<\/pre>\n
![\"Python](\"https:\/\/www.jquery-az.com\/wp-content\/uploads\/2017\/11\/61.2-Python-write.png\")
<\/p>\nUsing the append mode example<\/strong><\/h3>\n
# The example of append mode\r\n\r\nobjRead1 = open(\"readme.txt\", \"r\")\r\n\r\nContFile = objRead1.read();\r\n\r\nprint (\"Content before appending text : \", ContFile)\r\n\r\n\r\n# Closing the first instance\r\n\r\nobjRead1.close()\r\n\r\n#Open file in append mode\r\n\r\nobjAppend = open(\"readme.txt\", \"a\")\r\n\r\nobjAppend.write (\"Please dont remove the text..\\nJust add ahead of existing text! Thanks\")\r\n\r\n#Closing the file in append mode\r\n\r\nobjAppend.close()\r\n\r\n#Open and read after append(0\r\n\r\nobjRead2 = open(\"readme.txt\", \"r\")\r\n\r\nContAfterAppend = objRead2.read();\r\n\r\nprint (\"The content after append() : \", ContAfterAppend)\r\n\r\n\r\nobjRead2.close()<\/pre>\n
![\"append](\"https:\/\/www.jquery-az.com\/wp-content\/uploads\/2017\/11\/61.3-append-text-open.png\")
<\/p>\nReading only limited characters in the text file example<\/strong><\/h3>\n
# Read file with size\r\n\r\n\r\nobjFile = open(\"readme.txt\", \"r\")\r\n\r\nfileContent = objFile.read(10);\r\n\r\nprint (\"Reading limited data: \", fileContent)\r\n\r\n\r\nobjFile.close()<\/pre>\n
\nPython read line-by-line example<\/strong><\/h3>\n
# Read file line by line\r\n\r\nobjFile = open(\"readme.txt\", \"r\")\r\n\r\nfor linebyline in objFile:\r\n\r\n\u00a0\u00a0\u00a0 print(linebyline, end = '')\r\n\r\nobjFile.close()<\/pre>\n
\nAn example of readline() method to read line by line<\/strong><\/h3>\n
# Read file readline()\r\n\r\nobjFile = open(\"readme.txt\", \"r\")\r\n\r\nprint (objFile.readline());\r\n\r\nprint (objFile.readline());\r\n\r\n\r\nobjFile.close()<\/pre>\n
![\"readline\"](\"https:\/\/www.jquery-az.com\/wp-content\/uploads\/2017\/11\/61.4-readline.png\")
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