Python strings
- Strings are nothing but a set of characters.
- Strings in python are surrounded by either single quotation (
') marks, or double quotation marks ("). - Strings are immutable(i.e we can't update a part of the string)
first_name = 'Anjaneyulu'
last_name = "B"
multiline strings¶
we can create multiline strings using triple quotes.
description = '''
An apple is an edible fruit produced by an apple tree.
Apple trees are cultivated worldwide and are the most widely
grown species in the genus Malus.
The tree originated in Central Asia,
where its wild ancestor, Malus sieversii, is still found today.
'''
print(description)
using strings as arrays¶
- In python strings supports indexing.
- We can access string characters with index but can't be updated by the index number.
name = "Anji"
print(name[0])
# Output: A
iterate string with for loop¶
- we can iterate through strings
for x in "apple":
print(x)
find string length¶
- we can find string length with
lenfunction.
a = "Python is Awesome"
print(len(a))
# output: 17
using "in" operator with string¶
- we can use
inkeyword to check the substring.
sentense = "Apple is awesome fruit"
is_substring = "awesome" in sentense
print(is_substring)
# Output: True
using "not in" operator with string¶
- we can use
not inkeyword to check if the given substring not found in the given string.
sentense = "Apple is awesome fruit"
print("june" not in sentense)
# Output: True
slicing a string¶
we can return a range of characters by using the slice syntax. We need to specify the start and end indexes.
b = "awesome!"
print(b[2:5])
# output: eso
print(b[:5])
# output: aweso
print(b[2:])
# output: esome!
print(b[-5:-2])
# output: som
- if start index not specified then it will consider it as 0
- if end index is not specified then it will consider it as length of the string
- negative index is can also used in string slicing
convert string to upper case¶
uppermethod to convert the string to upper case
title = "Python is a programming language"
print(title.upper())
# output: PYTHON IS A PROGRAMMING LANGUAGE
convert string to lower case¶
lowermethod to convert the string to upper case
title = "Python is a programming language"
print(title.lower())
# output: python is a programming language
remove white space in the string¶
stripto remove the white space from start and end of the string.
name = " John "
print(name.strip())
# Output: John
replace part of the string¶
replaceto replace a substring with another string
s = "Jython is Awesome"
print(s.replace("J", "P"))
# Output: Python is Awesome
split string based on a seperator¶
splitmethod is used to split the string- it returns a list by splitting the string based on the seperator
- default seperator is space
title = "Google is a search engine"
print(title.split())
# Output: ['Google', 'is', 'a', 'search', 'engine']
concatenate strings¶
- combine two or more strings in to one
first_name = "Anji"
last_name = "B"
full_name = first_name + last_name
print(full_name)
# Output: AnjiB
format strings with place holders¶
formatmethod is used to format the string.
game = "cricket"
s = "I love to play {}"
print(s.format(game))
# Output: I love to play cricket
- we can use positions for place holders
string = "I placed an order with {2} items for {0} rupees. Exach item costs Rs.{1}."
print(string.format(100, "50", "three"))
# Output: I placed an order with three items for 100 rupees. Exach item costs Rs.50.
- we can also use names as place holders
string = "I placed an order with {item_count} items for {total} rupees. Exach item costs Rs.{item_cost}."
print(string.format(item_count="three", total=100, item_cost="50"))
# Output: I placed an order with three items for 100 rupees. Exach item costs Rs.50.
Escape characters in string¶
- we use
\to escape characters in the string.
s = "Software engineering is a \"difficult\" job to do."
print(s)
# Output: Software engineering is a "difficult" job to do.
- Find some of the escape characters below
| Code | Result |
|---|---|
| \' | Single Quote |
\\ | Backslash |
| \n | New Line |
| \r | Carriage Return |
| \t | Tab |
| \b | Backspace |
| \f | Form Feed |
| \ooo | Octal value |
| \xhh | Hex value |
string methods¶
| Method | Description |
|---|---|
| capitalize() | Converts the first character to upper case |
| casefold() | Converts string into lower case |
| center() | Returns a centered string |
| count() | Returns the number of times a specified value occurs in a string |
| encode() | Returns an encoded version of the string |
| endswith() | Returns true if the string ends with the specified value |
| expandtabs() | Sets the tab size of the string |
| find() | Searches the string for a specified value and returns the position of where it was found |
| format() | Formats specified values in a string |
| format_map() | Formats specified values in a string |
| index() | Searches the string for a specified value and returns the position of where it was found |
| isalnum() | Returns True if all characters in the string are alphanumeric |
| isalpha() | Returns True if all characters in the string are in the alphabet |
| isdecimal() | Returns True if all characters in the string are decimals |
| isdigit() | Returns True if all characters in the string are digits |
| isidentifier() | Returns True if the string is an identifier |
| islower() | Returns True if all characters in the string are lower case |
| isnumeric() | Returns True if all characters in the string are numeric |
| isprintable() | Returns True if all characters in the string are printable |
| isspace() | Returns True if all characters in the string are whitespaces |
| istitle() | Returns True if the string follows the rules of a title |
| isupper() | Returns True if all characters in the string are upper case |
| join() | Joins the elements of an iterable to the end of the string |
| ljust() | Returns a left justified version of the string |
| lower() | Converts a string into lower case |
| lstrip() | Returns a left trim version of the string |
| maketrans() | Returns a translation table to be used in translations |
| partition() | Returns a tuple where the string is parted into three parts |
| replace() | Returns a string where a specified value is replaced with a specified value |
| rfind() | Searches the string for a specified value and returns the last position of where it was found |
| rindex() | Searches the string for a specified value and returns the last position of where it was found |
| rjust() | Returns a right justified version of the string |
| rpartition() | Returns a tuple where the string is parted into three parts |
| rsplit() | Splits the string at the specified separator, and returns a list |
| rstrip() | Returns a right trim version of the string |
| split() | Splits the string at the specified separator, and returns a list |
| splitlines() | Splits the string at line breaks and returns a list |
| startswith() | Returns true if the string starts with the specified value |
| strip() | Returns a trimmed version of the string |
| swapcase() | Swaps cases, lower case becomes upper case and vice versa |
| title() | Converts the first character of each word to upper case |
| translate() | Returns a translated string |
| upper() | Converts a string into upper case |
| zfill() | Fills the string with a specified number of 0 values at the beginning |