Learning Python: Programming and Data Structures- Tutorial 12- String Manipulation

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Learning Python: Programming and Data Structures- Tutorial 12- String Manipulation

This example will demonstrate how you can do several things with strings.

1. Convert a string to Lower Case.

2. Convert a string to Upper Case

3. Capitalize a String

4. Slice substrings from a string

5. Find a particular substring in a string

6. Chop of leading and trailing characters from strings.

7. Find out the length of strings

8. Replace a substring by another.


# let us create a test string
testString1 = "Hello World!"
print "Original String: "+ testString1
# Print this string in lower case

# Converting a string to lower case
print "Converting to LowerCase"
print testString1.lower()

# Converting a string to upper case
print "Converting to Upper Case"
print testString1.upper()

# Capitalizing a string
# Only the first letter in the string will be capitalized
print "Capitalizing the String"
print testString1.capitalize()

# Trying to slice out a substring between given indexes
print "Substring from index 1 to 7"
print testString1[1:8]

#Substring from the start till character at index = 7 (start of string is index 0)
print "Substring from the start till character at index = 7 (start of string is index 0): "
print testString1[:8]

#Substring from the character at index = 7, till the end of the string (remember: start of string is index 0)
print "Substring from the character at index = 7, till the end of the string (remember: start of string is index 0): "
print testString1[7:]


#Find the position of a  substring within the string
#This gives us the first index during a left to right scan. If the string is not found, it returns -1
print "Find the index from which the substring 'llo' begins within the test string"
print testString1.find('llo')

print "Now, let's look for a substring which is not a part of the given string"
print testString1.find('xxy')

# Now, trying to find the index of a substring between specified indexes only
print "Now, trying to find a substring between specified indexes only: looking for 'l' between 4 and 9"
print testString1.find('l',4,9)

# rfind is used, to find the index from the reverse
# So, testString1.rfind('l') will look for the last index of l in the string
print "find('l') on the given string returns the following index (scanning the string from left to right):"
print testString1.find('l')

print "rfind('l') on the given string returns the following index (this scans the string from right to left):"
print testString1.rfind('l')

# Now let us try to replace/substitute a substring of this string with another string
print "Replacing World with Planet"
print testString1.replace("World","Planet")


# Now let us try to split the string, into separate words
# let us split it wherever there is a space
print "Splitting the string into words, wherever there is a space"
print testString1.split(" ")
print testString1.rsplit(" ")

# Remove leading and trailing whitespace characters
testString2 = "Hello World!  "
print "Current Test String=" + testString2
print "Length (there are whitespaces at the end):" + `len(testString2)`
print "Length after stripping "+ `len(testString2.strip())`

Output of the Program above:

Original String: Hello World!
Converting to LowerCase
hello world!
Converting to Upper Case
HELLO WORLD!
Capitalizing the String
Hello world!
Substring from index 1 to 7
ello Wo
Substring from the start till character at index = 7 (start of string is index 0):
Hello Wo
Substring from the character at index = 7, till the end of the string (remember: start of string is index 0):
orld!
Find the index from which the substring 'llo' begins within the test string
2
Now, let's look for a substring which is not a part of the given string
-1
Now, trying to find a substring between specified indexes only: looking for 'l' between 4 and 9
-1
find('l') on the given string returns the following index (scanning the string from left to right):
2
rfind('l') on the given string returns the following index (this scans the string from right to left):
9
Replacing World with Planet
Hello Planet!
Splitting the string into words, wherever there is a space
['Hello', 'World!']
['Hello', 'World!']
Current Test String=Hello World!
Length (there are whitespaces at the end):14
Length after stripping 12