Print string to text file

Question

In the following code, I want to substitute the value of a string variable TotalAmount into the text document, with Python:

text_file = open("Output.txt", "w")

text_file.write("Purchase Amount: " 'TotalAmount')

text_file.close()

How to do this?

Objectionable

why did you not do w+? – Giroux

@KarlKnechtel Your suggested duplicate seems to not include the essential part of actually writing the string to the file that is covered by this question and its answers. – Storer

@RyanM That's because OP already had code in the question for writing a string to a file, and the question (as I read it) isn't actually about writing the string. The problem is that the desired string isn't created properly. If it's supposed to be about both creating the string and writing it to the file, that needs more focus; and there are better duplicates about how to write to a file anyway. – Cofer

For that matter, one of the top-voted answers here even cites the duplicate I proposed. – Cofer

Answer 1

It is strongly advised to use a context manager. As an advantage, it is made sure the file is always closed, no matter what:

with open("Output.txt", "w") as text_file:
    text_file.write("Purchase Amount: %s" % TotalAmount)

This is the explicit version (but always remember, the context manager version from above should be preferred):

text_file = open("Output.txt", "w")
text_file.write("Purchase Amount: %s" % TotalAmount)
text_file.close()

If you're using Python2.6 or higher, it's preferred to use str.format()

with open("Output.txt", "w") as text_file:
    text_file.write("Purchase Amount: {0}".format(TotalAmount))

For python2.7 and higher you can use {} instead of {0}

In Python3, there is an optional file parameter to the print function

with open("Output.txt", "w") as text_file:
    print("Purchase Amount: {}".format(TotalAmount), file=text_file)

Python3.6 introduced f-strings for another alternative

with open("Output.txt", "w") as text_file:
    print(f"Purchase Amount: {TotalAmount}", file=text_file)

Upbringing

Assuming TotalAmount is an integer, shouldn't the "%s" be a "%d"? – Chasseur

@RuiCurado, if TotalAmount is an int, either %d or %s will do the same thing. – Upbringing

Great answer. I'm seeing a syntax error with a nearly identical use case: with . . .: print('{0}'.format(some_var), file=text_file) is throwing: SyntaxError: invalid syntax at the equal sign... – Lusk

@nicorellius, if you wish to use that with Python2.x you need to put from __future__ import print_function at the top of the file. Note that this will transform all of the print statements in the file to the newer function calls. – Upbringing

To make sure know what the variable type is often convert it to make sure, ex: "text_file.write('Purchase Amount: %s' % str(TotalAmount))" which will work with lists, strings, floats, ints, and anything else that is convertable to a string. – Bathilda

@EBo, format strings work slightly differently in different languages. In Python, %s means call obj.__str__. So it's identical behaviour to calling str explicitly. – Upbringing

agreed, but on the fly it is sometimes hard to know what to change when a diagnostic statement hickups. Also while I try to be consistent withthe variable type there is no guarantees. – Bathilda

@EBo, But it is guaranteed. If %s can't convert to a str, then str() can't either. If this isn't clear yet, perhaps you can open a new question about it. – Upbringing

I will have to track down an example where this worked for me. I may have misunderstood the issue and a solution that worked. What you say makes sense. – Bathilda

why did you not do w+? – Giroux

Answer 2

In case you want to pass multiple arguments you can use a tuple

price = 33.3
with open("Output.txt", "w") as text_file:
    text_file.write("Purchase Amount: %s price %f" % (TotalAmount, price))

More: Print multiple arguments in python

Variance

why did you not do w+? – Giroux

Just preference, I like to distinguish between when I'm writing and reading from a file. – Variance

Answer 3

If you are using Python3.

then you can use Print Function :

your_data = {"Purchase Amount": 'TotalAmount'}
print(your_data,  file=open('D:\log.txt', 'w'))

For python2

this is the example of Python Print String To Text File

def my_func():
    """
    this function return some value
    :return:
    """
    return 25.256


def write_file(data):
    """
    this function write data to file
    :param data:
    :return:
    """
    file_name = r'D:\log.txt'
    with open(file_name, 'w') as x_file:
        x_file.write('{} TotalAmount'.format(data))


def run():
    data = my_func()
    write_file(data)


run()

Salol

why did you not do w+? – Giroux

print(your_data, file=open(...)) will leave the file opened – Anemo

The best answer for python 3 because you can utilize features of print function. You don't need to map to str and concatenate elements, just give each element to print as parameters and let print function do the rest. Ex: print(arg, getattr(args, arg), sep=", ", file=output) – Boehmenism

Answer 4

With using pathlib module, indentation isn't needed.

import pathlib
pathlib.Path("output.txt").write_text("Purchase Amount: {}" .format(TotalAmount))

As of python 3.6, f-strings is available.

pathlib.Path("output.txt").write_text(f"Purchase Amount: {TotalAmount}")

Garrettgarrick

Answer 5

If you are using numpy, printing a single (or multiply) strings to a file can be done with just one line:

numpy.savetxt('Output.txt', ["Purchase Amount: %s" % TotalAmount], fmt='%s')

Hermaherman

Answer 6

I guess lots of people use the answers here as a general quick reference to how to write a string to a file. Quite often when I write a string to a file, I'd want to specify the file encoding and here is how to do it:

with open('Output.txt', 'w', encoding='utf-8') as f:
    f.write(f'Purchase Amount: {TotalAmount}')

If you don't specify the encoding, the encoding used is platform-dependent (see the docs). I think the default behavior is rarely useful from a practical point of view and could lead to nasty problems. That's why I almost always set the encoding parameter.

Isomerize

Answer 7

If you need to split a long HTML string in smaller strings and add them to a .txt file separated by a new line \n use the python3 script below. In my case I am sending a very long HTML string from server to client and I need to send small strings one after another. Also be careful with UnicodeError if you have special characters like for example the horizontal bar ― or emojis, you will need to replace them with others chars beforehand. Also make sure you replace the "" inside your html with ''

#decide the character number for every division    
divideEvery = 100

myHtmlString = "<!DOCTYPE html><html lang='en'><title>W3.CSS Template</title><meta charset='UTF-8'><meta name='viewport' content='width=device-width, initial-scale=1'><link rel='stylesheet' href='https://www.w3schools.com/w3css/4/w3.css'><link rel='stylesheet' href='https://fonts.googleapis.com/css?family=Lato'><link rel='stylesheet' href='https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css'><style>body {font-family: 'Lato', sans-serif}.mySlides {display: none}</style><body></body></html>"

myLength = len(myHtmlString)
division = myLength/divideEvery
print("number of divisions")
print(division)

carry = myLength%divideEvery
print("characters in the last piece of string")
print(carry)

f = open("result.txt","w+")
f.write("Below the string splitted \r\n")
f.close()

x=myHtmlString
n=divideEvery
myArray=[]
for i in range(0,len(x),n):
    myArray.append(x[i:i+n])
#print(myArray)

for item in myArray:
    f = open('result.txt', 'a')
    f.write('server.sendContent(\"'+item+'\");' '\n'+ '\n')

f.close()

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