#!/usr/bin/env python
# coding: utf-8

# ## ``Q8.`` ##    
# 
# ## ```Using Regular Expressions, develop a Python program to``` ##    
# 
# ## ```a) Identify a word with a sequence of one upper case letter followed by lower case letters. ``` ##     
# 
# ## ```b) Find all the patterns of '1(0+)1' in a given string. ``` ##   
# 
# ## ```c) Match a word containing 'z' followed by one or more o's.``` ##    
# 
# ## ```Prompt the user for input. ``` ## 

# ## -----------------------------------------------------------------------------------------------------------------------------

# **Approach to identify a sequence of one upper case letter followed by lower case letters**
# 
# To check if the sequence of one upper case letter followed by lower case letters we use regular expression ` [A-Z]+[a-z]+$`   
# 
# **Approach to find the patterns of `1(0+)1` in a given string**    
# 
# A string contains patterns of the form `1(0+)1` where `(0+)` represents any non-empty consecutive sequence of 0's. 
# 
# First compile a pattern which follows `1(0+)1` using re.compile(regex) method. Search a first sub-string in original string which follows `1(0+)1` pattern using `pattern.search(string)` method.
# 
# `substr = pattern.search(string)` returns `None` if it doesn't find the given regex as sub-string in original string otherwise it returns first matched sub-string which follows `1(0+)1` pattern.   
# 
# `substr.start()` gives us starting index of matched regex and `substr.end()` gives us ending index of matched regex.
# Whenever we find regex as sub-string then increase count by 1 and again search for given regex starting from ending index of previous sub-string. *__The patterns are allowed to overlap.__*
# 
# **Approach to match a word consisting of `z` followed by one or more `o's`**
# 
# Compile a pattern which follows `zo+\w*`, that matches a word which contains `'z'` followed by one or more `o's`.  
# 
# Then pass a string to the `findall()` method. This method returns the list of the matched strings. If the length of this list is equal to zero then it doesn't contain a matched string.
# 
# `\w` `->` `represents any letter, numeric digit, or the underscore character.`  
# 
# `*` `->` `means zero or more occurrence of the character.`  
# 
# `+` `->` `means one or more occurrence of the character.`  

# ## -----------------------------------------------------------------------------------------------------------------------------

# In[19]:


import re


# Function to Find all the patterns of "1(0+)1" in a given string
def check_uc_lc_pattern(user_input):
    # regex
    pattern = re.compile("[A-Z]+[a-z]+$")

    # searching pattern
    if pattern.search(user_input):
        print("String pattern match success \n")
    else:
        print("String fails the pattern \n")


def count_pattern(user_input):
    # search regex '10+1' in original string search() function return first occurrence
    # of regex '10+1' otherwise None '10+1' means sub-string starting and ending with 1
    # and at least 1 or more zeros in between
    count = 0
    pattern = re.compile("10+1")
    substr = pattern.search(user_input)

    # search for regex in original string until we are done with complete string
    while substr != None:
        # if we find any occurrence then increase count by 1
        count = count + 1

        # find next occurrence just after previous sub-string for first occurrence of the pattern
        user_input = user_input[(substr.end() - 1) :]
        substr = pattern.search(user_input)
    print(f"The number of times the pattern appears in the string is {count} \n")


def z_followed_by_o(user_input):
    # Regex \w * zo+\w * will match text that contains 'z', followed by one or more 'o'
    pattern = re.compile("zo+\w*")

    # The findall() method returns all matching strings of the regex pattern
    match_object = pattern.findall(user_input)

    # If length of match_object is not equal to zero then it contains matched string
    if len(match_object) != 0:
        print("String pattern match success \n")
    else:
        print("No match \n")


def menu():
    while True:
        print(
            "1 --> Identify a word with a sequence of one upper case letter followed by lower case letters"
        )
        print("2 --> Find all the patterns of '1(0+)1' in a given string")
        print("3 --> Match a word containing 'z' followed by one or more o's")
        print("4 --> Exit the program")
        choice = int(input("Enter a number to perform any of the operation: "))
        print("\n")
        if choice == 1:
            user_input = input(
                "Enter a string with a sequence of Upper and Lower case letters: "
            )
            print("\n")
            check_uc_lc_pattern(user_input)
        elif choice == 2:
            user_input = input("Enter a string in the form of 1(0+)1 pattern: ")
            print("\n")
            count_pattern(user_input)
        elif choice == 3:
            user_input = input("Enter a string: ")
            print("\n")
            z_followed_by_o(user_input)
        else:
            break


# Main
if __name__ == "__main__":
    menu()