File I/O

# EXECUTE THIS ONE FIRST!

import os

# Constants for the exercises:
WORKING_DIR = os.getcwd()
DATA_DIR = os.path.join(os.path.dirname(WORKING_DIR), 'data')

1. Sum numbers listed in a file

Fill ____ pieces of the code below. sum_numbers_in_file function takes a input file path as argument, reads the numbers listed in the input file and returns the sum of those numbers. You can assume that each line contains exactly one numeric value.

def sum_numbers_in_file(input_file):
    sum_ = 0  # A common way to use variable names that collide with built-in/keyword words is to add underscore
    with ____(input_file, ____) as ____:
        for line in ____:
            ____ = line.strip()  # Remove potential white space 
            ____ += float(____)
    return ____

in_file = os.path.join(DATA_DIR, 'numbers.txt')
assert sum_numbers_in_file(in_file) == 189.5

---------------------------------------------------------------------------
UnboundLocalError                         Traceback (most recent call last)
Cell In[3], line 2
      1 in_file = os.path.join(DATA_DIR, 'numbers.txt')
----> 2 assert sum_numbers_in_file(in_file) == 189.5

Cell In[2], line 3, in sum_numbers_in_file(input_file)
      1 def sum_numbers_in_file(input_file):
      2     sum_ = 0  # A common way to use variable names that collide with built-in/keyword words is to add underscore
----> 3     with ____(input_file, ____) as ____:
      4         for line in ____:
      5             ____ = line.strip()  # Remove potential white space 

UnboundLocalError: local variable '____' referenced before assignment

2. Reading first word from each line of a file

Implement find_first_words function which takes an input file path as argument. The function should find the first word of each line in the file and return these words as a list. If a line is empty, the returned list should contain an empty string for that line.

# Your implementation here

in_file1 = os.path.join(DATA_DIR, 'simple_file.txt')
in_file2 = os.path.join(DATA_DIR, 'simple_file_with_empty_lines.txt')

expected_file_1 = ['First', 'Second', 'Third', 'And']
assert find_first_words(in_file1) == expected_file_1

expected_file_2 = ['The', '', 'First', 'nonsense', '', 'Then']
assert find_first_words(in_file2) == expected_file_2