How do i read the first row of a text file in python?

Question

Lots of other answers here, but to answer precisely the question you asked (before @MarkAmery went and edited the original question and changed the meaning):

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Use the read() Function to Read the First Line of a File in Python
Use the readline() Function to Read the First Line of File in Python
Use the readlines() Function to Read the First Line of a File in Python
Use the next() Function to Read the First Line of a File in Python
Related Article - Python File
How do I read the first line of a text file in Python?
How do you read a specific row in a text file in Python?
How do I read the first few lines of a file in Python?
How do you extract specific parts of a text file in Python?

>>> f = open('myfile.txt')
>>> data = f.read()
>>> # I'm assuming you had the above before asking the question
>>> first_line = data.split('\n', 1)[0]

In other words, if you've already read in the file (as you said), and have a big block of data in memory, then to get the first line from it efficiently, do a split() on the newline character, once only, and take the first element from the resulting list.

Note that this does not include the \n character at the end of the line, but I'm assuming you don't want it anyway (and a single-line file may not even have one). Also note that although it's pretty short and quick, it does make a copy of the data, so for a really large blob of memory you may not consider it "efficient". As always, it depends...

HowTo
Python How-To's
Read First Line of a File in Python

Created: January-18, 2021

Use the read() Function to Read the First Line of a File in Python
Use the readline() Function to Read the First Line of File in Python
Use the readlines() Function to Read the First Line of a File in Python
Use the next() Function to Read the First Line of a File in Python

In Python, we have built-in functions that can handle different file operations. A Text file contains a sequence of strings in which every line terminated using a newline character \n.

In this tutorial, we will learn how to read the first line of a text file in Python.

We can use the open() function to create a file object by passing the file path to the function and open a file in a specific mode, read mode by default.

Use the read() Function to Read the First Line of a File in Python

The read() function is used to read the data from a file. To extract the first line from the file, we can simply use the split() function to get a list of all the lines separated based on the newline character, and extract the first line from this list. For example:

with open("sample.txt") as f:
    lines = f.read() ##Assume the sample file has 3 lines
    first = lines.split('\n', 1)[0]

print(first)

Output:

Sample File Line 1

Use the readline() Function to Read the First Line of File in Python

Another method to read the first line of a file is using the readline() function that reads one line from the stream.

with open("sample.txt") as f:
    firstline = f.readline().rstrip()

print(firstline)

Output:

Sample File Line 1

Notice that we use the rstrip() function to remove the newline character at the end of the line because readline() returns the line with a trailing newline.

Use the readlines() Function to Read the First Line of a File in Python

We can also use the readlines() function, which reads all the lines from the file and returns a list of each line as the list item, and then extract the first line from the returned list. For example:

with open("sample.txt") as f:
    firstline = f.readlines()[0].rstrip()
    
print(firstline)

Output:

Sample File Line 1

Use the next() Function to Read the First Line of a File in Python

An unconventional method of achieving the same is by using the next() function. It returns the next item in an iterator. So if we pass the file object to the next() function, it returns the first line of the file. For example:

with open("sample.txt") as f:
    firstline = next(f)
    
print(firstline)

Output:

Sample File Line 1

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Text files are composed of plain text content. Text files are also known as flat files or plain files. Python provides easy support to read and access the content within the file. Text files are first opened and then the content is accessed from it in the order of lines. By default, the line numbers begin with the 0th index. There are various ways to read specific lines from a text file in python, this article is aimed at discussing them.

File in use: test.txt

Method 1: fileobject.readlines()

A file object can be created in Python and then readlines() method can be invoked on this object to read lines into a stream. This method is preferred when a single line or a range of lines from a file needs to be accessed simultaneously. It can be easily used to print lines from any random starting index to some ending index. It initially reads the entire content of the file and keep a copy of it in memory. The lines at the specified indices are then accessed.

Example:

Python3

file = open('test.txt')

content = file.readlines()

print("tenth line")

print(content[9])

print("first three lines")

print(content[0:3])

Output

tenth line

This is line 10.
first three lines

This is line 1.This is line 2.This is line 3.

Method 2: linecache package

The linecache package can be imported in Python and then be used to extract and access specific lines in Python. The package can be used to read multiple lines simultaneously. It makes use of cache storage to perform optimization internally. This package opens the file on its own and gets to the particular line. This package has getline() method which is used for the same.

Syntax:

getLine(txt-file, line_number)

Example:

Python3

import linecache

particular_line = linecache.getline('test.txt', 4)

print(particular_line)

Output :

This is line 5.

Method 3: enumerate()

The enumerate() method is used to convert a string or a list object to a sequence of data indexed by numbers. It is then used in the listing of the data in combination with for loop. Lines at particular indexes can be accessed by specifying the index numbers required in an array.

Example:

Python3

file = open("test.txt")

specified_lines = [0, 7, 11]

for pos, l_num in enumerate(file):

if pos in specified_lines:

print(l_num)

Output

This is line 1.
This is line 8.
This is line 12.

How do I read the first line of a text file in Python?

Use the read() Function to Read the First Line of a File in Python..

Use the readline() Function to Read the First Line of File in Python..

Use the readlines() Function to Read the First Line of a File in Python..

Use the next() Function to Read the First Line of a File in Python..

How do you read a specific row in a text file in Python?

Use readlines() to Read the range of line from the File You can use an index number as a line number to extract a set of lines from it. This is the most straightforward way to read a specific line from a file in Python. We read the entire file using this way and then pick specific lines from it as per our requirement.

How do I read the first few lines of a file in Python?

Use file..

a_file = open("file_name.txt") Open "file_name.txt".

number_of_lines = 3..

for i in range(number_of_lines): Print the first number_of_lines lines of a_file..

line = a_file. readline().

print(line).

How do you extract specific parts of a text file in Python?

How to extract specific portions of a text file using Python.

Make sure you're using Python 3..

Reading data from a text file..

Using "with open".

Reading text files line-by-line..

Storing text data in a variable..

Searching text for a substring..

Incorporating regular expressions..

Putting it all together..

programming python Read Python

How do i read the first row of a text file in python?

Use the read() Function to Read the First Line of a File in Python

Use the readline() Function to Read the First Line of File in Python

Use the readlines() Function to Read the First Line of a File in Python

Use the next() Function to Read the First Line of a File in Python

Related Article - Python File

Python3

Python3

Python3

How do I read the first line of a text file in Python?

How do you read a specific row in a text file in Python?

How do I read the first few lines of a file in Python?

How do you extract specific parts of a text file in Python?

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