Python Read List of Strings From File

Storing information in files lets you proceed a record of the data with which a program is working. This means you lot don't take to generate information over again when working with a program. You lot only read that data from a file.

To read files, use the readlines() method. Once you lot've read a file, you use split() to plow those lines into a list.

In this guide, we discuss how to use the carve up() method to read a text file into a list. We'll refer to an example so you can get started reading text files into lists quickly.

Python: Read Text File into List

Permit's start with a text file called grilled_cheese.txt. This file contains the ingredients for a grilled cheese sandwich. Our file content looks like this:

2 tbsp, ricotta ane tbsp, grated parmesan 50g, mozzarella 25g, gorgonzola 2, thick slices white bread i tbsp, butter

The outset column in our file contains the quantity of each ingredient to be used. The second column contains the name of an ingredient.

We read this file into our code using the open() and readlines() methods:

with open("grilled_cheese.txt", "r") as grilled_cheese: 	lines = grilled_cheese.readlines() 	print(lines)

In our code, nosotros open up a file called "grilled_cheese.txt" in read way. Read manner is denoted by the "r" grapheme in our open up() statement. Next, nosotros print those lines to the console.

Let's run into what our Python code returns:

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['2 tbsp, ricotta\due north', 'ane tbsp, grated parmesan\n', '50g, mozzarella\n', '25g, gorgonzola\due north', '2, thick slices white breadstuff\n', '1 tbsp, butter\due north']

Our code returns a listing of each line in our file. This is not quite the output nosotros are expecting. While we've read our file into a list, we have a problem: each line is stored in its own string. Ingredients and their quantities are not divide.

Divide Values into a List

To solve this problem, we use the dissever() method. This method lets us divide a string using a separator character we specify.

To beginning, we declare two lists: quantities and ingredients. This code will remain indented because it is part of our open() cake of code.

            quantities = [] 	ingredients = []

Nosotros'll iterate over our list so nosotros can access each line of text from our file. And so nosotros'll split each line into two parts. The dividing betoken is the comma followed past a infinite on each line:

for fifty in lines: 		 as_list = l.split up(", ") 		 quantities.append(as_list[0]) 		 ingredients.suspend(as_list[1])

The for loop lets united states read our file line by line. The first value in "as_list" is the quantity of an ingredient. The second value is the name of the ingredient. Nosotros then print both of these lists to the console:

            print(quantities) 	impress(ingredients)

Allow'south run our code:

['2 tbsp, ricotta\north', '1 tbsp, grated parmesan\n', '50g, mozzarella\n', '25g, gorgonzola\n', '2, thick slices white bread\n', 'i tbsp, butter\northward'] ['2 tbsp', '1 tbsp', '50g', '25g', '2', '1 tbsp'] ['ricotta\n', 'grated parmesan\n', 'mozzarella\northward', 'gorgonzola\n', 'thick slices white bread\n', 'butter\n']

Our code prints iii lists to the console. The beginning listing is a listing of all the lines of text in our file. The second list contains all the quantities from our file. The third listing contains all the ingredients.

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Remove New Lines

There is still one comeback that nosotros need to make. Every ingredient ends in the "\n" character. This character denotes a new line. Nosotros can remove this character past using the replace() method:

for l in lines: 	   	  as_list = l.split(", ") 		  quantities.append(as_list[0]) 		  ingredients.append(as_list[i].replace("\n", ""))

In our for loop, nosotros replace the value "\northward" with an empty string. We do this on the as_list[1] value which correlates to the name of each ingredient.

Now that we've made this change, our plan is ready:

with open("grilled_cheese.txt", "r") as grilled_cheese: 	   lines = grilled_cheese.readlines()  	   quantities = [] 	   ingredients = []  	   for fifty in lines: 	  			 as_list = 50.split(", ") 			     quantities.append(as_list[0]) 			     ingredients.append(as_list[1].replace("\n", ""))  	   print(quantities) 	   print(ingredients)

Let's run our code and meet what happens:

['two tbsp', '1 tbsp', '50g', '25g', '2', 'ane tbsp'] ['ricotta', 'grated parmesan', 'mozzarella', 'gorgonzola', 'thick slices white bread', 'butter']

Our lawmaking successfully transforms our text file into 2 lists. One list contains the quantities of ingredients for a recipe. The other list contains the ingredients nosotros'll apply for the recipe.

Conclusion

You lot tin can read a text file using the open() and readlines() methods. To read a text file into a list, employ the divide() method. This method splits strings into a listing at a certain graphic symbol.

In the case above, we dissever a string into a list based on the position of a comma and a space (", "). Now you're set up to read a text file into a listing in Python like an skilful.

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Source: https://careerkarma.com/blog/python-read-text-file-into-list/

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