Learning Python Strings: Replace, Join, Split, Reverse

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In Python everything is object and string are an object too. Python string can be created simply by enclosing characters in the double quote.
For example:
var = "Hello World!"
In this tutorial, we will learn -

Accessing Values in Strings

Python does not support a character type, these are treated as strings of length one, also considered as substring.
We use square brackets for slicing along with the index or indices to obtain a substring.
For example:
var1 = "Guru99!"
var2 = "Software Testing"
print "var1[0]:",var1[0]
print "var2[1:5]:",var2[1:5]
When the above code is executed, it gives the result
Var1[0]: G
Var2[1:5]: oftw

Various String Operators

There are various string operators that can be used in different ways like concatenating different string.
Suppose if a=guru and b=99 then a+b= "guru99". Similarly, if you are using a*2, it will "GuruGuru". Likewise, you can use other operators in string.
Operator
Description
Example
[]Slice- it gives the letter from the given indexa[1] will give "u" from the word Guru as such ( 0=G, 1=u, 2=r and 3=u)
x="Guru"
print x[1]
[ : ]Range slice-it gives the characters from the given rangex [1:3] it will give "ur" from the word Guru. Remember it will not consider 0 which is G, it will consider word after that is ur.
x="Guru" 
print x[1:3]
inMembership-returns true if a letter exist in the given stringu is present in word Guru and hence it will give 1 (True)
x="Guru" 
print "u" in x
not inMembership-returns true if a letter exist is not in the given stringl not present in word Guru and hence it will give 1
x="Guru" 
print "l" not in x
r/RRaw string suppresses actual meaning of escape characters.Print r'\n' prints \n and print R'/n' prints \n
% - Used for string format%r - It insert the canonical string representation of the object (i.e., repr(o)) %s- It insert the presentation string representation of the object (i.e., str(o)) %d- it will format a number for displayThe output of this code will be "guru 99".
name = 'guru'
number = 99
print'%s %d' % (name,number)
+It concatenates 2 stringsIt concatenate strings and gives the result
x="Guru" 
y="99" 
print x+y
*RepeatIt prints the character twice.
x="Guru" 
y="99" 
print x*2

Some more examples

You can update Python String by re-assigning a variable to another string. The new value can be related to previous value or to a completely different string all together.
x = "Hello World!"
print x[:6] 
print x[0:6] + "Guru99"
Note : - Slice:6 or 0:6 has the same effect

Python String replace() Method

The method replace() returns a copy of the string in which the values of old string have been replaced with the new value.
oldstring = 'I like Guru99' 
newstring = oldstring.replace('like', 'love')
print(newstring)

Changing upper and lower case strings

In Python, you can even change the string to upper case or lower case.
string="python at guru99"
print string.upper()
Output for this will be "PYTHON AT GURU99."
Likewise, you can also do for other function as well like capitalize
string="python at guru99"  
print string.capitalize()
The output will be "Python at guru99."
You can also convert your string to lower case
string="PYTHON AT GURU99""
print string.lower()
The output will be "python at guru99"

Using "join" function for the string

The join function is a more flexible way for concatenating string. With join function, you can add any character into the string.
For example, if you want to add a colon (:) after every character in the string "Python" you can use the following code.
print":".join("Python")
The output will be
P:y:t:h:o:n

Reversing String

By using the reverse function, you can reverse the string. For example, if we have string "12345" and then if you apply the code for the reverse function as shown below.
string="12345"  
print''.join(reversed(string))
It will give the output "54321."

Split Strings

Split strings is another function that can be applied in Python let see for string "guru99 career guru99". First here we will split the string by using the command word.split and get the result.
word="guru99 career guru99"  
print word.split(' ')
The output will be ['guru99', 'career', 'guru99']
To understand this better we will see one more example of split, instead of space (' ') we will replace it with ('r') and it will split the string wherever 'r' is mentioned in the string
word="guru99 career guru99"  
print word.split('r')
The output will be ['gu', 'u99 ca', 'ee', ' gu', 'u99']
Important Note:
In Python, Strings are immutable.
Consider the following code
x = "Guru99"
x.replace("Guru99","Python")
print x
will still return Guru99. This is because x.replace("Guru99","Python") returns a copy of X with replacements made
You will need to use the following code to observe changes
x = "Guru99"
x = x.replace("Guru99","Python")
print x
Python has introduced a .format function which does way with using the cumbersome %d and so on for string formatting.

Summary:

Since Python is an object-oriented programming language, many functions can be applied to Python objects. A notable feature of Python is its indenting source statements to make the code easier to read.
  • Accessing values through slicing - square brackets are used for slicing along with the index or indices to obtain a substring.
    • In slicing, if range is declared [1:5], it can actually fetch the value from range [1:4]
  • You can update Python String by re-assigning a variable to another string
  • Method replace() returns a copy of the string in which the occurrence of old is replaced with new.
    • Syntax for method replace: oldstring.replace("value to change","value to be replaced")
  • String operators like [], [ : ], in, Not in, etc. can be applied to concatenate the string, fetching or inserting specific characters into the string, or to check whether certain character exist in the string
  • Other string operations include
    • Changing upper and lower case
    • Join function to glue any character into the string
    • Reversing string
    • Split string

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