Question

using python

The following shows the result of calling function read_from_file_sum_squares() for each of these two files: >>> from praco import read_from_file_sum_squares >>> read_from_file_sum_squares () Enter the filename: file1 9 >>> read_from_file_sum_squares () Enter the filename: file2 14 20 1 >>> You can use file = open(filename, "r") to open the file named by string filename to read, and the line list_lines = file.readlines() to store in list_lines the list of strings, where each string is a line of the file, in the order they appear in the file. Remember to close the file once you do not need it anymore, using file.close(). Exercise 4 In this exercise you will practice nested iterations and building lists of lists. Add a Python function read_from_file_table() to the praco.py file that reads a file as before, and stores every non-negative number in each line in a list, in the order provided, obtaining a table (i.e., a list of lists). If a line is empty, it should add the empty list as an element of the table. For the two file above, the result is as follows: >>> from praco import read_from_file_table >>> read_from_file_table() Enter the filename: file1 [[3]] >>> read_from_file_sumtable() Enter the filename: file2 [[1, 2], [4, 2], [], [1]] >>>

Answer 1

Hello!

# is used comment in python

list is the collection which is changable similar to array

map is used to map all the elements to the list variable

input() is used to get input in string format

split() is used to split all the elemets

rstrip() is used to strip '\n' and spaces

And i have explained more clearly using comments.

CODE:

def read_from_file_table():
        # declare list of lists
        list_of_lists=[]
        # asks the user to enter file name
        fname=input("Enter the filename:")+".txt"
        # open file for read only
        f=open(fname,"r")
        # reads all the lines in the file
        filedata=f.readlines()
        # iterates over each line
        for eachline in filedata:
            # strips new line and splits all the numbers
            line=eachline.rstrip().split()
            # creates a list with empty elememts
            list_for_each_line=[]
            # iterates over every element in the line
            for number in line:
                # if the number is greater than 0 
                if(int(number)>=0):
                    # then only it wll append
                    list_for_each_line.append(int(number))
            # finally appens the list of the line to list of lists
            list_of_lists.append(list_for_each_line)
        # prints the list of lists
        print(list_of_lists)

# this code helps us to not let run immediately after import
# whenever function is called only it will executed
if __name__ == "__main__":
    read_from_file_table()

praco.py - C:/Users/DELL/Desktop/New folder/praco.py (3.8.3) File Edit Format Run Options Window Help def read from file table(): # declare list of lists list of lists=[] # asks the user to enter file name fname=input("Enter the filename:")+".txt" # open file for read only f=open(fname, "r") # reads all the lines in the file filedata=f.readlines () # iterates over each line for eachline in filedata: # strips new line and splits all the numbers line=eachline.rstrip().split() # creates a list with empty elements list_for_each_line=[] # iterates over every element in the line for number in line: # if the number is greater than 0 if(int (number)>=0): # then only it wll append list_for_each_line.append(int (number)) # finally appens the list of the line to list of lists list_of_lists.append(list_for_each_line) # prints the list of lists print (list_of_lists) # this code helps us to not let run immediately after import # whenever function is called only it will executed if "main": read_from_file_table() name ==

TEXT FILE:

fIle1.txt

1 2 3
4 5
6

-8 -9 99
33

Luahan La file1 - Notepad File Edit Format View Help 1 2 3 4 5 6 -8 -9 99 33

OUTPUT:

ch = New folder Python 3.8.3 Shell Х File Edit Shell Debug Options Window Help Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:20:19) [MSC v.1925 32 bit (In tel)] on win32 Type "help", "copyright", "credits" or "license ()" for more information. >>> == RESTART: C:/Users/DELL/Desktop/New folder/praco.py Enter the filename:filel [[1, 2, 3], [4, 5], [6], [], [99], [33]] >>> from praco import read_from_file_table >>> read_from_file_table() Enter the filename:filel [[1, 2, 3], [4, 5], [6], [], [99], [33]] >>> |

Hope this helps and clear.

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