Python Basics 2 - String Methods, Place Holders and raw_input

Basics of Python (String Methods, raw_input & Place Holders)

Strings

Strings are sequences of characters without inherent values but can contain meaningful characters.
- Example:
  - print 'That's a pretty bad string'
- Syntax error occurs due to unescaped single quote.

Common Backslash Commands

Specific characters can be inserted into strings using backslash commands:
- \ - Inserts a backslash
- \n - Inserts a new line
- \t - Inserts a tab space

String Examples

Escaping Characters:
- Using backslash to include an apostrophe:
  - Example: print 'That\'s a pretty GOOD string'
  - Output: That's a pretty GOOD string
New Lines:
- Using \n for line breaks:
  - Example: print 'This string\nis on multiple lines'
  - Output: This string is on multiple lines
Tabs:
- Using \t for tab spaces:
  - Example: print 'This string\thas a tab.'
  - Output: This string has a tab.

String Indexes

Each character in a string has an index, starting from 0.
- Example:
  - For string dog = 'I am Sam', the character positions are:
    - I (0) a (1) m (2) S (3) a (4) m (5)
Access characters using their index:
- dog[0] returns I
- dog[3] returns S

Accessing String Characters

You can access string characters using index numbers:
- Example:
  - dog = 'This is a Sample String'
    - print dog[0] outputs T
    - print dog[7] outputs i

Storing String Characters in Variables

Characters can be stored in variables:
- Example:
  - cat = dog[0] (stores the first character T).
  - print cat outputs T

String Methods

Python offers various methods to manipulate strings:
- len(dog) - Calculates the length of the string
- dog.upper() - Converts string to uppercase
- dog.lower() - Converts string to lowercase
- Example of method usage:
  - length = len(dog)
  - big = dog.upper()
  - small = dog.lower()

String Concatenation

Concatenation is the process of joining strings using the + operator:
- Example:
```
who = 'I '
do = 'like to eat '
what = 'pizza!'
print who + do + what
```
The output will be: I like to eat pizza!

Type Casting in Concatenation

Non-string variables must be casted to strings:
- Example:
  - pi = 3.1415
  - ```
  print 'I like to eat ' + str(pi) + '!'
```
- Output: I like to eat 3.1415!

Obtaining User Input with raw_input

Use raw_input() to get user input:
- Example:
  - name = raw_input('What is your name?')
  - When user inputs 'Sam', it outputs:
    - Your name is Sam

Casting User Input

Raw input is returned as a string; convert to int or float if necessary:

Example:

first_numb = raw_input('First Number?')
second_numb = raw_input('Second Number?')
product = int(first_numb) * int(second_numb)
print 'Their product is ' + str(product)

Inputting 5 and 12 outputs: Their product is 60.

String Formatting with %

Use placeholders for formatting strings:
- %s (string), %f (float), %d (integer)

Example:

string_1 = 'Camelot'
string_2 = 'place'
print "Let's not go to %s. 'Tis a silly %s." % (string_1, string_2)

Outputs: Let's not go to Camelot. 'Tis a silly place.