Why are the functions I have set up not working in python?

Question

I am fairly new to python and I am trying to figure out why my functions aren't giving me the output I am looking for. I feel like I have tried everything and tried researching, but I haven't found anything that has helped me.

Here is my code:

from sys import argv                    

def GetCharactersWords(input):
    characters = input.read()
    words = len(characters.split())              
    #word = len(words)
    return words

def GetCharacterNumber(input):
    characters = input.read()
    number = characters.count(".")       
    return number                            

def FirstSentence(input):
    characters = input.read()           
    fields = characters.split(".")        
    field1 = fields[0]                  
    return field1


def LengthFirstSentence(input):
    characters = input.read()
    fields = characters.split(".")
    field1 = fields[0]
    field0 = len(field1)
    return field0

def LastSentence(input):
    characters = input.read()
    fields = characters.split(".")
    field2 = fields[-1]
    return field2                  


def LengthLastSentence(input):
    characters = input.read()
    fields = characters.split(".")
    field3 = fields[-1]                  
    field4 = len(field3)
    return field4


def print_to_file(word_characters, number_characters, first_sentence, length_first,
last_sentence, length_last):
    with open("output.txt", "w") as outfile: 
        outfile.write("Here is the text file: " + '\n') 
        outfile.write(str(input) + '\n')               
        outfile.write("Number of words in the file?" + '\n')  
        outfile.write(str(word_characters) + '\n')
        outfile.write("Number of sentences in the file?" + '\n')
        outfile.write(str(number_characters) + '\n')
        outfile.write("First sentence in the file?" + '\n')
        outfile.write(str(first_sentence) + '\n')
        outfile.write("Last sentence in the file?" + '\n')
        outfile.write(str(last_sentence) + '\n')
        outfile.write("Length of the first sentence" + '\n')
        outfile.write(str(length_first)+ '\n')
        outfile.write("Length of the last sentence" + '\n')
        outfile.write(str(length_last) + '\n')
        outfile.close()                             



def main(argv):                         
    script = argv[0]                    
    filename = argv[1]                  
    input = open(filename, "r")       
    word_characters = GetCharactersWords(input)
    number_characters = GetCharacterNumber(input)
    first_sentence = FirstSentence(input)
    length_first = LengthFirstSentence(input)
    last_sentence = LastSentence(input)
    length_last = LengthLastSentence(input)
    file_print = print_to_file(word_characters, number_characters, first_sentence, length_first,
    last_sentence, length_last)



if __name__ == '__main__':
        main(argv)

Here is the output it gives me:

Here is the text file: 
<built-in function input>
Number of words in the file?
2430
Number of sentences in the file?
0
First sentence in the file?

Last sentence in the file?

Length of the first sentence
0
Length of the last sentence
0

I can't figure out why it isn't giving me the different outputs.

Thanks for any help!

Each of your functions reads the entire file, leaving the current file position at the very end of the file - so every function you call after the first one has nothing to read. Either reopen the file each time, rewind it to the start via `.seek(0)`, or read the file once in `main()` and pass the contents to each function. (Note that `input` was a bad name for the file, as that's overriding a Python built-in function). — jasonharper, Oct 07 '20 at 03:12
Does this answer your question? [Python: Why a file is empty after reading it and writing to another one?](https://stackoverflow.com/questions/28320658/python-why-a-file-is-empty-after-reading-it-and-writing-to-another-one) — wjandrea, Oct 07 '20 at 03:14
or these? [Re-open files in Python?](https://stackoverflow.com/q/2106820/4518341) [Why can't I call read() twice on an open file?](https://stackoverflow.com/q/3906137/4518341) — wjandrea, Oct 07 '20 at 03:14
BTW, welcome to SO! Check out the [tour], and [ask] if you want advice. For example, making a [mre] is super helpful. You posted a lot of code, most of which is not relevant to the problem. — wjandrea, Oct 07 '20 at 03:16

score 1 · Accepted Answer · answered Oct 07 '20 at 03:17

There are a few problems with your code. The biggest one is that you're not reading the file properly. When you open a file with open(), you can only read() the file once. Calling read() will read the entire file and empty the stream, so a second call to read() will only give you an empty string, which is why only the "Number of words" has a non-empty result.

Instead, you should call read() once to read the contents, and pass the contents of the file directly instead of the file handle to your functions. For example:

# Take characters directly instead of a file
def FirstSentence(characters):
    fields = characters.split(".")        
    field1 = fields[0]                  
    return field1

def main(argv):                         
    script = argv[0]                    
    filename = argv[1]                  
    characters = open(filename, "r").read()
    word_characters = GetCharactersWords(characters) # and so on

Additionally, "<built-in function input>" is printed for the file contents because when you printed it, input has not been assigned, so it ends up printing the built-in function input instead. As others have pointed out, input is a bad variable name as it overrides the built-in input function. If you had chosen some other name instead, it would have resulted in a NameError.

Why are the functions I have set up not working in python?

1 Answers1