06_string_functions.py

#======================================================================================
#                                   STRING FUNCTIONS
#======================================================================================


#======================================================================================
# 1) types
#--------------------------------------------------------------------------------------
      # a) type()  ---built-in function    / output:type (like str, int, float, bool)
      # b) str()   ---built-in function    / output:string
#======================================================================================

#--------------------------------------------------------------------------------------
# a) type(value)--returns the data type of a value.
#--------------------------------------------------------------------------------------
name = "Bob"
print(type(name))
age = 25
print(type(age))
# print("Your age is:" + age) #can't combine a string with an integer using + operator.

#--------------------------------------------------------------------------------------
# b) str(value)--converts any value into string value.
#--------------------------------------------------------------------------------------
# Here the age is converted to str only in this print statement.
print("Your age is:"+str(age))
print(type(age))  # we can also check that the data type is not changed.

# This is how we convert the int data type to str using str function.
age = str(age)
print(type(age))  # We can also check that the data type is changed.
# Python is flexible with Data Types.

#======================================================================================
# 2) Math
#--------------------------------------------------------------------------------------
      # a) len()    ---built-in function    /output:int
      # b) count() ---str method           /output:int
#======================================================================================

#--------------------------------------------------------------------------------------
# a) len(value)--returns the no of characters in string, it counts everything even spaces.
#--------------------------------------------------------------------------------------
password = "2580mun "
print(len(password))
#--------------------------------------------------------------------------------------
# b) count(substring)--returns how often a word appears in the string.
#--------------------------------------------------------------------------------------
text = """
Python is easy to learn.
Python is powerful.
Many people love python.
"""
print(text.count("Python"))  # the output is 2 because the Python is case-sensitive.

#======================================================================================
# 3) Transformations
#--------------------------------------------------------------------------------------
      # a) replace()                      ----str method
      # b) concatenation ex:'H' + 'i'     ----operator   /output:string
      # c) f_string(f{})                  ----operator
      # d) split()                        ----str method /output:list of strings
      # e) string repetition ex:'ha'*2    ----operator   /output:string
      # f) indexing ex:'cat'[0]           ----operator /output:string
      # g) slicing ex:'cat'[1:3]          ----operator /output:string
#======================================================================================
#--------------------------------------------------------------------------------------
# a) replace(old, new) --swaps part of the text with something new.
#--------------------------------------------------------------------------------------
phone = "630-1701-800"
print(phone.replace("-", ""))

ph = "+49 (176) 123-4567"
print(ph.replace("+", "").replace(" ",
      "").replace("(", "").replace(")", "").replace("-", ""))
#--------------------------------------------------------------------------------------
# b) concatenations --Joins two strings into one.
#--------------------------------------------------------------------------------------
first_name = "Bob"
last_name = "Smith"
full_name = first_name + " " + last_name
print(full_name)

folder = "C:/Users/Smith/"
file = "reports.csv"
full_file_path = folder + file
print(full_file_path)

#--------------------------------------------------------------------------------------
# c) f-string(f{})--"f" stands for "formatted",it lets you easily put variables and 
# expressions directly inside string value.
#--------------------------------------------------------------------------------------
name = "Bob"
age = "25"
is_student = False

print("My Name is", name, "I am", age,
      "year Old and Student status is", is_student)  # Hard to read
print("My Name is " + name, "I am "+str(age) +
      " years Old and Student status is " + str(is_student))  # Hard to read

#--------------------------------------------------------------------------------------
# f-string:shorter, cleaner, easier to read!.
# variables in f-string.
#--------------------------------------------------------------------------------------
print(f"My Name is {name} I am {age} years Old and Student status is {is_student}")
print(f"2 + 3 = {2+3}")  # expressions in f-string.
# printing curly braces using double {{}} curly braces.
print(f"Hello {{Welcome to Python}}")

#--------------------------------------------------------------------------------------
# d) split(separator)-- breaks a string into smaller parts.
#--------------------------------------------------------------------------------------
csv_file = "123,Max,USA, 1970-10-05,M"
print(csv_file.split(","))
stamp = "2025-01-19"
print(stamp.split("-"))

#--------------------------------------------------------------------------------------
# e) string * number ---repeats the string multiple times.
#--------------------------------------------------------------------------------------
print("Ha "*3)
print("**"*10)


#--------------------------------------------------------------------------------------
# In Python, indexing and slicing are the ways to access
# parts of sequence such as strings, lists, tuple, etc.
#--------------------------------------------------------------------------------------
# f) Indexing
#--------------------------------------------------------------------------------------
#     indexing means accessing one single element from a sequence using its
#     position number(index)
#--------------------------------------------------------------------------------------
# imp rule **Python index starts from 0
#         **Negative indexing starts from -1 (last element)
#--------------------------------------------------------------------------------------
text = "Python"
#------------------------------------------------
# Value | #positive-index   |  #Negative-index  |
#------------------------------------------------
#  p    |     0             |      -6           |
#  y    |     1             |      -5           |
#  t    |     2             |      -4           |
#  h    |     3             |      -3           |
#  o    |     4             |      -2           |
#  n    |     5             |      -1           |
#------------------------------------------------

# extracting the first character using +ve and -ve index number
print(text[0])
print(text[-6])

# extracting the last character using +ve and -ve index number
print(text[5])
print(text[-1])

# extract h
print(text[3])


#--------------------------------------------------------------------------------------
# g) Slicing
#--------------------------------------------------------------------------------------
#     slicing means extracting multiple elements (a portion) from a sequence.
#     Syntax:- sequence[start:end:step].
#     start:starting index (include).
#     end:ending index (excluded).
#     step:gap between elements (optional).
#--------------------------------------------------------------------------------------
date = "2025-01-19"
# extract the year
print(date[0:4])
# if you leave the start index empty, python starts form index 0
print(date[:4])

# extract the month
print(date[5:7])

# extract the day
print(date[8:])
print(date[-2:])

#--------------------------------------------------------------------------------------
# when to use positive or negative index.
#--------------------------------------------------------------------------------------
# Use Positive index if you want to extract part from the left side (start) of a string.
# Use Negative index if you want to extract part from the right side (end) of a string.
#--------------------------------------------------------------------------------------


#======================================================================================
# 4 Cleaning
#--------------------------------------------------------------------------------------
# ----------------------------------------------
#     Clean WhiteSpaces
# ----------------------------------------------
#           a) lstrip()  ---str method     /output:string
#           b) rstrip()  ---str method     /output:string
#           c) strip()   ---str method     /output:string
# ----------------------------------------------
#     Clean Cases
# ----------------------------------------------
#           d) lower()   ---str method     /output:string
#           e) upper()  ---str method     /output:string
#======================================================================================

#--------------------------------------------------------------------------------------
# Whitespace Cleanup
#--------------------------------------------------------------------------------------

#--------------------------------------------------------------------------------------
# a) lstrip()--removes spaces from the left side of a string.
#--------------------------------------------------------------------------------------
text = "    Engineering".lstrip()
print(text, len(text))

#--------------------------------------------------------------------------------------
# b) rstrip()--removes spaces from the right side of a string
#--------------------------------------------------------------------------------------
text = "Engineering   ".rstrip()
print(text, len(text))

#--------------------------------------------------------------------------------------
# c) strip()--removes spaces from both ends
#--------------------------------------------------------------------------------------
text = "   Engineering   ".strip()
print(text, len(text))

# only removes spaces at the start or end, not in the middle
text = "Data Engineering".strip()
print(text, len(text))

# it removes any characters you want from the start and end - not just spaces
text = "###ABC###".strip("#")
print(text, len(text))

# How to check the quality of the data
text = "  Engineering  ".strip()
print(len(text))
print(len(text.strip()))
no_of_spaces = len(text) - len(text.strip())
is_clean = len(text) == len(text.strip())
print(f"No of Spaces: {no_of_spaces}")
print(f"Is my Data Clean?:{is_clean}")

# Best Practice-- Trim Spaces form User input.

#--------------------------------------------------------------------------------------
# Cases Conversions
#--------------------------------------------------------------------------------------

#--------------------------------------------------------------------------------------
# d)lower()--makes all letters lowercase.
#--------------------------------------------------------------------------------------
text = "python PROGRAMMING"
print(text.lower())

#--------------------------------------------------------------------------------------
# e)upper()--makes all letters uppercase.
#--------------------------------------------------------------------------------------
print(text.upper())

search = "Email"
data = "email"
print(search == data)

# use case:- Clean Data for Matching
# Lowercase all text to prevent case-based mismatches during search or comparison.

search = "Email".lower()
data = "eMaiL".lower()
print(search == data) # True


search = "  Email".lower()
data = "eMail   ".lower()
print(search == data) # False

# Best Practice - Clean before search
# Always trim spaces and lowercase your data and search them before matching.
search = "  Email".lower().strip()
data = "eMail   ".lower().strip()
print(search == data)

#--------------------------------------------------------------------------------------
# Python Challenge
# expected out put: name:maria | role: data engineer | age: 27.
#--------------------------------------------------------------------------------------
s = "968-Maria ( D@t@ Engineer );; 27y"
clean = s.replace("968-", "").replace("@", "a").replace("(","").replace(")", "").replace(";", "").replace("y", "")
print(clean)
parts = clean.split()
print(parts)
name = parts[0].lower()
role = parts[1].lower() + " "+parts[2].lower()
age = parts[3]
print(f"name: {name} | role: {role} | age: {age}")

#======================================================================================
# 5 Search
#--------------------------------------------------------------------------------------
#     a) startswith()    ---str method   /output:boolean
#     b) endswith()      ---str method   /output:boolean
#     c) 'a' in 'cat'    ---operator     /output:boolean
#     d)find()           ---str method   /output:number
#======================================================================================

ph = "+91-630-1701-800"

#--------------------------------------------------------------------------------------
# a) startswith(substring)--checks if the string begins with a specific word.
#--------------------------------------------------------------------------------------
print(ph.startswith("630"))
print(ph.startswith("+91"))

#--------------------------------------------------------------------------------------
# b) endswith(substring)--checks if the string ends with a specific word.
#--------------------------------------------------------------------------------------
file = "report.csv"
print(file.endswith("rst"))
print(file.endswith(".csv"))

#--------------------------------------------------------------------------------------
# c) 'substring' in 'sting' -- checks if a word exists in the string.
#--------------------------------------------------------------------------------------
email = "BobSmith@gmail.com"
print("j" in email)
print("@" in email)

#--------------------------------------------------------------------------------------
# d)find(substring)--returns the starting position of a word in the string.
#--------------------------------------------------------------------------------------
text = "python programming"
print(text.find("program"))


phone1 = "+48-176-12345"
phone2 = "48-654-16548"
phone3 = "0048-654-16548"

# Extract only phone number without country code.
# Hardcoding the start position doesn't work  when the country code length changes.
print(phone1[4:])
print(phone2[3:])
print(phone3[5:])

# Extracting only phone numbers with out country code by using find.
# print(phone1.find("-"))
# print(phone2.find("-"))
# print(phone3.find("-"))

print(phone1[phone1.find("-")+1:])
print(phone2[phone2.find("-")+1:])
print(phone3[phone3.find("-")+1:])
# find() is great when combined with other methods to add dynamics


#======================================================================================
# 6) Validation
#--------------------------------------------------------------------------------------
#     a) isalpha()   ---str method   /output:boolean
#     b) isnumeric() ---str method   /output:boolean
#======================================================================================

#--------------------------------------------------------------------------------------
# a) isalpha()--checks if the string has only letters.
#--------------------------------------------------------------------------------------
country = "USA"
print(country.isalpha())

country = "USA1"
print(country.isalpha())

#--------------------------------------------------------------------------------------
# b) isnumeric()--checks if the string has only numbers.
#--------------------------------------------------------------------------------------
phone = "0987612345"
print(phone.isnumeric())
# . and - considered as special character that's why it is showing false in output
phone = "123-456-789"
print(phone.isnumeric())

price = "4.50"
print(price.isnumeric())