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

# # RE module

# In[1]:


import re
import numpy as np


# ### 1. To extract a pattern in a given string - Use `re.findall(pattern, text)`
# 
# Returns a list containing all matches.
# 
# In the example below we try to extract string of three consecutive numbers.

# In[2]:


text = 'Jeswin 619 George 999 98Y Y27J0 JK871'
re.findall(r'\d{3}', text)


# Now to get the first or last patterns use indexing.

# In[3]:


re.findall(r'\d{3}', text)[0]


# In[4]:


re.findall(r'\d{3}', text)[-1]


# ### 2. To substitute a pattern with a string of your choice - `re.sub(pattern, desired_string, text)`
# 
# replaces the matches with the text of your choice.

# In[5]:


text = 'Jeswin 619 George 999 98Y Y27J0 JK871'


# To replace __Y__ with string __B__.

# In[6]:


re.sub('Y', "B", text)


# In the given text, ensure that the alpha-numeric words doesnt have alphabets and resulting numeric word must have only numerics and must have length of 3 (You can use any numeric of your choice).

# In[7]:


output = []
for word in text.split():
    if re.findall(r'\d', word):
        if re.findall(r'[A-Z]',word):
            word = re.sub(r'[A-Z]', '5', word)
            if len(word)==3:
                output.append(word)
            elif len(word)<3:
                while (3-len(word))<=0:
                    word += str(np.random.randomint(9))
                output.append(word)
            elif len(word)>3:
                word = word[:3-len(word)]
                output.append(word)
        else:
            output.append(word)
                
    else:
        output.append(word)




# In[8]:


output


# Combining the list of words to a single sentence using [string join()](https://www.geeksforgeeks.org/python-string-join-method/).

# In[9]:


' '.join(output)


# In[10]:


text


# # Reference
# 
# ![](images/1.PNG)
# 
# ![](images/2.PNG)
# 
# ![](images/3.PNG)