Python Read File

The read() method is a Python file method that reads the contents of a file and returns a string of the contents of the file.

Related course: Complete Python Programming Course & Exercises

syntax

file.read(size)

Parameters

Parameter Description Remarks

  • size Reads the number of bytes in the file The positive integer parameter can be omitted. When omitted, the entire document is read in one sitting.

return value

  • Reads the file and returns the value of the string type.

You can use these functions:

#Read everything in the text, return string
read()

#Read only the first line of text, return one string
readline()

#reads everything in the text and returns list
readlines()

read() in Python

Size omitted, read the entire document in one sitting. File to be read demo.txt.

python code

data = open("demo.txt", "r").read()
print(data)

Read bytes from file

File to be read: demo.txt. Suppose we want to read only 30 bytes of data.

data = open("demo.txt", "r").read(30)
print(data)

File to be read: demo.txt

Reading empty file

The read method returns an empty string when size is equal to 0.

data = open("demo.txt", "r").read(0)
print(data)
print(type(data))
print(len(data))

Implementation results.

<class 'str'>\
0

read(), readline(), readlines()

In order to distinguish the difference between the read(), readline(), and readlines() functions in python, we use the python instance to see

First create a file /tmp/week.txt that reads.

$ cat /tmp/week.txt
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday

Then go to the python parser.

[user@linux ~]# python
Python 2.6.6 (r266:84292, Nov 22 2013, 12:16:22) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.

>>>> f=open('/tmp/week.txt','rb') #Open /tmp/week.txt file in read mode
>>> f.read() #call the read() function
'Monday\nTuesday\nWednesday\nThursday\nFriday\nSaturday\nSunday\n' #Back to results

>>> f.readline() #call the readline() function
'Monday\n' #Back to results

>>> f.readlines() #call the readlines() function
['Tuesday\n', 'Wednesday\n', 'Thursday\n', 'Friday\n', 'Saturday\n', 'Sunday\n'] #Back to results