Match exact phrase within a string in Python

Question

I\'m trying to determine whether a substring is in a string. The issue I\'m running into is that I don\'t want my function to return True if the substring is found within an

Answer 1

One can do this very literally with a loop

phrase = phrase.lower()
text = text.lower()

answer = False 
j = 0
for i in range(len(text)):
    if j == len(phrase):
        return text[i] == " "
    if phrase[j] == text[i]:
        answer = True
        j+=1
    else:
        j = 0 
        answer = False 
return answer

Or by splitting

phrase_words = phrase.lower().split()
text_words = text.lower().split()

return phrase_words in text_words

or using regular expressions

import re
pattern = re.compile("[^\w]" + text + ""[^\w]")
pattern.match(phrase.lower())

to say that we want no characters preceding or following our text, but whitespace is okay.

Answer 2

Since your phrase can have multiple words, doing a simple split and intersect won't work. I'd go with regex for this one:

import re

def is_phrase_in(phrase, text):
    return re.search(r"\b{}\b".format(phrase), text, re.IGNORECASE) is not None

phrase = "Purple cow"

print(is_phrase_in(phrase, "Purple cows make the best pets!"))   # False
print(is_phrase_in(phrase, "Your purple cow trampled my hedge!"))  # True

Answer 3

Regular Expressions should do the trick

import re

def is_phrase_in(phrase, text):
    phrase = phrase.lower()
    text = text.lower()
    if re.findall('\\b'+phrase+'\\b', text):
        found = True
    else:
        found = False
    return found

Answer 4

Using PyParsing:

import pyparsing as pp

def is_phrase_in(phrase, text):
    phrase = phrase.lower()
    text = text.lower()

    rule = pp.ZeroOrMore(pp.Keyword(phrase))
    for t, s, e in rule.scanString(text):
      if t:
        return True
    return False

text = "Your purple cow trampled my hedge!"
phrase = "Purple cow"
print(is_phrase_in(phrase, text))

Which yields:

True

Answer 5

Here you go, hope this helps

 # Declares
 string = "My name is Ramesh and I am cool. You are Ram ?"
 sub = "Ram"

 # Check String For SUb String
 result = sub in string

 # Condition Check
 if result:

    # find starting position
    start_position = string.index(sub)

    # get stringlength
    length = len(sub)

    # return string
    output = string[start_position:len]