python_string_methods.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# A Few Python String Methods with Examples\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 38,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Note: All string methods returns new values. They do not change the original string.\n",
    "\n",
    "# https://www.w3schools.com/python/python_ref_string.asp"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String capitalize() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The capitalize() method returns a string where the first character is upper case.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hello, and welcome to my world!\n"
     ]
    }
   ],
   "source": [
    "# Converts the first character to upper case\n",
    "\n",
    "txt = \"hello, And Welcome To My World!\"\n",
    "\n",
    "x = txt.capitalize()\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String casefold() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The casefold() method returns a string where all the characters are lower case.\n",
    "\n",
    "This method is similar to the lower() method, but the casefold() method is stronger, more aggressive, meaning that it will convert more characters into lower case, and will find more matches when comparing two strings and both are converted using the casefold() method.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "hello, and welcome to my world!\n"
     ]
    }
   ],
   "source": [
    "# Converts string into lower case\n",
    "\n",
    "txt = \"Hello, And Welcome To My World!\"\n",
    "\n",
    "x = txt.casefold()\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String center() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The center() method will center align the string, using a specified character (space is default) as the fill character.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "       banana       \n"
     ]
    }
   ],
   "source": [
    "# Returns a centered string\n",
    "\n",
    "txt = \"banana\"\n",
    "\n",
    "x = txt.center(20)\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String count() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The count() method returns the number of times a specified value appears in the string."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "2\n"
     ]
    }
   ],
   "source": [
    "# Returns the number of times a specified value occurs in a string\n",
    "\n",
    "txt = \"I love apples, apple are my favorite fruit\"\n",
    "\n",
    "x = txt.count(\"apple\")\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String encode() Method"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n"
     ]
    }
   ],
   "source": [
    "# UTF-8 encode the string:\n",
    "\n",
    "txt = \"My name is Ståle\"\n",
    "\n",
    "x = txt.encode()\n",
    "\n",
    "print()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String endswith() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The encode() method encodes the string, using the specified encoding. If no encoding is specified, UTF-8 will be used.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n"
     ]
    }
   ],
   "source": [
    "# Check if the string ends with a punctuation sign (.):\n",
    "\n",
    "txt = \"Hello, welcome to my world.\"\n",
    "\n",
    "x = txt.endswith(\".\")\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String expandtabs() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The expandtabsize() method sets the tab size to the specified number of whitespaces."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "H e l l o\n"
     ]
    }
   ],
   "source": [
    "# Set the tab size to 2 whitespaces:\n",
    "\n",
    "txt = \"H\\te\\tl\\tl\\to\"\n",
    "\n",
    "x =  txt.expandtabs(2)\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String find() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The find() method finds the first occurrence of the specified value.\n",
    "\n",
    "The find() method returns -1 if the value is not found.\n",
    "\n",
    "The find() method is almost the same as the index() method, the only difference is that the index() method raises an exception if the value is not found. (See example below)\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "7\n"
     ]
    }
   ],
   "source": [
    "# Where in the text is the word \"welcome\"?:\n",
    "\n",
    "txt = \"Hello, welcome to my world.\"\n",
    "\n",
    "x = txt.find(\"welcome\")\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String index() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The index() method finds the first occurrence of the specified value.\n",
    "\n",
    "The index() method raises an exception if the value is not found.\n",
    "\n",
    "The index() method is almost the same as the find() method, the only difference is that the find() method returns -1 if the value is not found. (See example below)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "7\n"
     ]
    }
   ],
   "source": [
    "# Where in the text is the word \"welcome\"?:\n",
    "\n",
    "txt = \"Hello, welcome to my world.\"\n",
    "\n",
    "x = txt.index(\"welcome\")\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String isalnum() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The isalnum() method returns True if all the characters are alphanumeric, meaning alphabet letter (a-z) and numbers (0-9).\n",
    "\n",
    "Example of characters that are not alphanumeric: (space)!#%&? etc."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "False\n"
     ]
    }
   ],
   "source": [
    "# Check if all the characters in the text are alphanumeric:\n",
    "\n",
    "txt = \"Company#$@12\"\n",
    "\n",
    "x = txt.isalnum()\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String isalpha() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The isalpha() method returns True if all the characters are alphabet letters (a-z).\n",
    "\n",
    "Example of characters that are not alphabet letters: (space)!#%&? etc."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n"
     ]
    }
   ],
   "source": [
    "# Check if all the characters in the text are letters:\n",
    "\n",
    "txt = \"zeeshan\"\n",
    "\n",
    "x = txt.isalpha()\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String isdecimal() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The isdecimal() method returns True if all the characters are decimals (0-9).\n",
    "\n",
    "This method is used on unicode objects."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 32,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n"
     ]
    }
   ],
   "source": [
    "# Check if all the characters in the unicode object are decimals:\n",
    "\n",
    "txt = \"\\u0033\" # unicode for 3\n",
    "\n",
    "x = txt.isdecimal()\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String isdigit() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The isdigit() method returns True if all the characters are digits, otherwise False.\n",
    "\n",
    "Exponents, like ², are also considered to be a digit.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n"
     ]
    }
   ],
   "source": [
    "# Check if all the characters in the text are digits:\n",
    "\n",
    "txt = \"50800\"\n",
    "\n",
    "x = txt.isdigit()\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python String isidentifier() Method\n",
    "\n",
    "Definition and Usage\n",
    "\n",
    "The isidentifier() method returns True if the string is a valid identifier, otherwise False.\n",
    "\n",
    "A string is considered a valid identifier if it only contains alphanumeric letters (a-z) and (0-9), or underscores (_). A valid identifier cannot start with a number, or contain any spaces."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 36,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n"
     ]
    }
   ],
   "source": [
    "# Check if the string is a valid identifier:\n",
    "\n",
    "\n",
    "txt = \"Demoo\"\n",
    "\n",
    "x = txt.isidentifier()\n",
    "\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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