Python 计算字符串的出现次数并打印包含它们的行，以及打印字符串出现的次数，带有多个子句

Question

I've been trying to create a python script that takes in two inputs, a file name and a string. Once it takes those in, it is supposed to print out the number of occurrences of the input string, as well as each line that contains the input string.

I am also required to not use lists, the split method, python string methods, the keyword "in", and i may only use indexing to access the first character of a string, and slicing to get the tail of the string.

What I've done so far:

def main():
  search_for = raw_input("What term would you like to search for?")
  text_file_name = raw_input("Which file would you like to search in?")
  count_text_file(search_for, text_file_name)




def count_text_file(search_for, text_file_name):
   usersFile = open(text_file_name, 'r')
   usersTermLength = len(search_for)
   usersFileLength = len(text_file_name)

   occurenceOfString = 0

    while i<usersFileLength:
        firstChar = usersFile[i]
        if firstChar==searchFor[0]:
            indexUsersTermLength = usersTermLength + i #end slice
            possibleMatch = usersFile[i:indexUsersTermLength]
            if possibleMatch == searchFor:
                print #the entire line
                occurenceOfString+=1
                i+=1
            else: 
                i+=1
        else:
            i+=1

Answer 1

A few issues in your code.

usersFileLength = len(text_file_name)

That's just the length of the name of the file. Not the size of the file's contents.

firstChar = usersFile[i]

This is not how you read from a file. You need to use a function likeread() .

Also, you break a couple of the (silly) constraints. Here's my solution. It reads the entire file then goes through it char-by char. It builds the current word and when it reaches a non-letter it compares.

def count_text_file(search_for, text_file_name):
    with open(text_file_name, 'r') as users_file:
        # Read entire file
        content = users_file.read()
        line_number = 1
        # Build the words of the file char-by-char
        current_word = ""
        while len(content) > 0:
            # "only use indexing to access the first character of a string"
            c = content[0]
            # If it's a letter add to string
            # Can't use c.isalpha() as it is a "python string method"
            if (c >= 'A' and c <= 'Z') or (c >= 'a' and c <= 'z'):
                current_word += c
            # Else (not a letter), check the word
            else:
                if current_word == search_for:
                    print(f"found at line {line_number}")
                if c == '\n':
                    line_number += 1
                # Reset for next word
                current_word = ""
            # "only use ... slicing to get the tail of the string"
            content = content[1:]

There are some improvements you can do. For example, words with punctuation in them won't be found (ex: "can't" or "non-existent"). Also, it only considers a "letter" to be "[A-Za-z]". Unicode characters won't be recognized. And it is case sensitive. But since this is an assignment, who knows if your teacher cares about any of that.