2.7.1. Python Strings#

Defination: A string is a sequence of characters. Strings are immutable. Strings are enclosed in single quotes or double quotes.

2.7.1.1. Creating a string#

We can create a string by enclosing characters in quotes. Python treats single quotes the same as double quotes.

# Example 1
str1 = 'Hello World'
print(str1)

Hello World

2.7.1.2. Assigning a string#

Defination: Assigning a string to a variable is called string assignment.

# Example 2
str2 = "Hello World"
print(str2)

Hello World

2.7.1.3. Multiline Strings#

Defination: We can assign a multiline string to a variable by using three quotes.

# Example 3
str3 = """Hello World
This is a multiline string"""
print(str3)

Hello World
This is a multiline string

# Example 4: using single quotes
str4 = '''Hello World
This is a multiline string'''
print(str4)

Hello World
This is a multiline string

2.7.1.4. Slice Strings#

Defination: We can access substrings, by using the slice syntax.

Slicing of strings is done by using the slice operator ( [ ] and [ : ] ) with indexes starting at 0 in the beginning of the string and working their way from -1 at the end.

#Example 5
str5 = "Hello World"
print(str5[0:5])

Hello

2.7.1.5. Slice from the start#

Defination: By leaving out the start index, the range will start at the first character.

# Example 6
str6 = "Hello World"
print(str6[:5])

Hello

2.7.1.6. Slice to the end#

Defination: By leaving out the end index, the range will go to the end.

# Example 7
str7 = "Hello World"
print(str7[6:])

World

2.7.1.7. Negative Indexing#

Defination: Negative indexing means beginning from the end, -1 refers to the last item, -2 refers to the second last item etc.

# Example 8
str8 = "Hello World"
print(str8[-5:-2])

Wor

2.7.1.8. Modify Strings#

Defination: We cannot change the value of a string. We can only assign a new string to the same name.

# Example 9
str9 = "Hello World"
str9[0] = 'J'
print(str9)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In [9], line 3
      1 # Example 9
      2 str9 = "Hello World"
----> 3 str9[0] = 'J'
      4 print(str9)

TypeError: 'str' object does not support item assignment

2.7.1.9. String Upper Case#

Defination: We can convert a string into upper case by using upper() method.

Syntax of upper() method with parameters: string.upper()

# Example 10
str10 = "Hello World"
print(str10.upper())

HELLO WORLD

2.7.1.10. String Lower Case#

Defination: We can convert a string into lower case by using lower() method.

Syntax of lower() method with parameters: string.lower()

# Example 11
str11 = "Hello World"
print(str11.lower())

hello world

2.7.1.11. String Replace#

Defination: We can replace a string with another string by using replace() method.

Syntax of replace() method with parameters: string.replace(old, new)

Parameters:

  1. old: old substring to be replaced.

  2. new: new substring to be replaced.

# Example 12
str12 = "Hello World"
print(str12.replace("H", "J"))

Jello World

2.7.1.12. String Remove Whitespace#

Defination: We can remove whitespace from the beginning or the end of a string by using strip() method.

Syntax of strip() method with parameters: string.strip()

# Example 13
str13 = " Hello World "
print(str13.strip())

Hello World

2.7.1.13. String Split#

Defination: We can split a string into substrings by using split() method.

Syntax of split() method with parameters: string.split(separator, maxsplit)

Parameters:

  1. separator: The is a delimiter. The string splits at this specified separator. If is not specified, any whitespace (space, newline etc.) string is a separator.

  2. maxsplit: It is a number, which tells us to split the string into maximum of provided number of times. If it is not provided then there is no limit.

# Example 14
str14 = "Hello World"
print(str14.split(" "))

['Hello', 'World']

2.7.1.14. String Concatenation#

Defination: We can concatenate strings by using + operator.

# Example 15
str15 = "Hello"
str16 = "World"
str17 = str15 + str16
print(str17)

HelloWorld

2.7.1.15. String Format#

Defination: We can format strings by using format() method.

Syntax of format() method with parameters: string.format(value1, value2, …)

# Example 16
str18 = "Hello"
str19 = "{} World"
print(str19.format(str18))

Hello World

2.7.1.15.1. String Format with Position#

Defination: We can format strings by using format() method with position. The position is the index of the argument in the format() method. The index starts from 0.

# Example 17
str20 = "Hello"
str21 = "Charan"
str22 = "{0} this is {1}"
print(str22.format(str20, str21))

Hello this is Charan

2.7.1.15.2. String Format with Keyword#

Defination: We can format strings by using format() method with keyword.

# Example 18
str23 = "Hello"
str24 = "Charan"
str25 = "{greeting} this is {name}"
print(str25.format(greeting = str23, name = str24))

Hello this is Charan

2.7.1.15.3. String Format with Variable#

Defination: We can format strings by using format() method with variable.

# Example 19
str26 = "Hello"
str27 = "Charan"
str28 = "{greeting} this is {name}"
print(str28.format(greeting = str26, name = str27))

Hello this is Charan

2.7.1.16. String Escape Character#

Defination: We can use escape character to insert characters that are illegal in a string.

# Example 20
str29 = "My name is \"Charan\""
print(str29)

My name is "Charan"

2.7.1.17. Escape Character:#

  1. ‘ Single Quote

  2. \ Backslash

  3. \n New Line

  4. \r Carriage Return

  5. \t Tab

  6. \b Backspace

  7. \f Form Feed

  8. \ooo Octal value

  9. \xhh Hex value