Chapter 2: Python Strings Manipulation

Concatenation :

concatenate using '+' operator

prefix = "al"
suffix = "pha"
print(prefix + suffix) # output : alpha

f-String:

helpful to print message with variable values.

syntax: f" your message {var_a} and print {var_b} "

prefix = "al"
suffix = "pha"
print(f"This is prefix: {prefix} and this is suffix: {suffix}") 
#output: This is prefix: al and this is suffix: pha

Repetition:

Repeat string x no of times using '*' operator

prefix = "al"
suffix = "pha"
print((prefix + suffix)*2) # output : alphaalpha

Indexing:

starts from 0, access element using index value

prefix = "al"
suffix = "pha"
print(prefix[0]) # output : a
print(prefix[1]) # output: h

Slicing:

slice(stop)

      blog_name = "python recall"
      sliced_string = blog_name[slice(4)]
      print(sliced_string) # output: pyth

slice(start, stop, step)

start at given index, then stop at given index while jumping by step value.

Step is optional parameter if don't want to jump
- ```
      blog_name = "python recall"
      sliced_string = blog_name[slice(2,12,2)]
      print(sliced_string) # output: to ea
```

[:]

up to given index[:], while excluding given value.

eg: index[3] , will return 0,1,2 and excludes 3

      blog_name = "python recall"
      sliced_string = blog_name[:3]
      print(sliced_string) # output: pyt

[-i]

starts from last index towards 0.

e.g: -1 is last index value of string

      blog_name = "python recall"
      sliced_string = blog_name[-3]
      print(sliced_string) # output: a

Reverse [::-1]

Reverse the string and return

      blog_name = "python recall"
      sliced_string = blog_name[::-1]
      print(sliced_string) # output: llacer nohtyp

String Functions

There is huge list of string functions available but these are few we should be able to keep top of mind.

capitalize, count, endswith, find, index, isalnum, isalpha, isdecimal, isdigit, isidentifier, islower, isnumeric, isspace, istitle, isupper, join, lower, partition, replace, split, startswith, strip, title, upper, sorted

We are going to use this code to learn all these functions.

book_name = "art of intrusion Version"
version = "v02"
price = "25"
discount="3.95"
publication_house = "pyhouse"

Function	code	Output	Note
capitalize	`book_name.capitalize()`	Art of intrusion version	First letter is capitalize
count	`book_name.count(i)`	3
endswith	`book_name.endswith('ion')`	True	If string ends with given value
find	`book_name.find('ion')`	13	if not found, return -1
index	`book_name.index('ion')`	13	if does not exist, error
isalnum	`book_name.isalnum()`	False	only a-z & numbers No-space, No-characters
isalpha	`book_name.isalpha()`	False	a-z, A-Z, no space, no characters
isdecimal	`price.isdecimal()`	True	only numbers with in 0-9 , no space, valid(254) invalid(456.32)
isdigit	`price.isdigit()`	True	T if all numbers(124) F(Hello123, 2.52, ' ', 1/2)

islower	`book_name.islower()`	False	T/F all lower?
isnumeric	`price.isnumeric()`	True	all #, no space/char/float
isspace	`book_name.isspace()`	False	all whitespace ?
istitle	`book_name.istitle()`	False	all string titlecase ?
isupper	`book_name.isupper()`	False	all char uppercase ?
join	`' '.join( ['hello','python'] )`	hello python	join and return 1 string
partition	`book_name.partition('rus')`	('art of int', 'rus', 'ion Version')	partition at given value , first occurrence'''
replace	`book_name.replace('art','Art')`	Art of intrusion Version
startswith	`book_name.startswith('ar')`	True	return if string starts with given value
strip	`book_name.strip()`	art of intrusion Version	remove leading, trailing space
upper	`book_name.upper()`	ART OF INTRUSION VERSION	all uppercase
title	`book_name.title()`	Art Of Intrusion Version	all words title case, first char capital only
sorted	`sorted(publication_house)`	['e', 'h', 'o', 'p', 's', 'u', 'y']	sorted list return
	`sorted(publication_house, reverse=True)`	['y', 'u', 's', 'p', 'o', 'h', 'e']	reverse sort

you may find isalnum, isalpha, isdigit confusing, just to revise.

isalnum() e.g: abc123 isalpha() e.g: abc isdigit() e.g: 123

Strings Manipulation -ch-02