Python challenge: Exploring strings

Here are some functions that can be applied on strings. Let’s take “lorem ipsum” as a dummy example:

lorem = "lorem ipsum"

Printing a string

print("Dummy string:  ", lorem)

Getting the length of a string

print("Length: ",len(lorem))

Capitalize a string

print("Capitalized: " + lorem.capitalize())

Checking if a string ends in a certain way

print("endswith 'ipsum': " + str(lorem.endswith("ipsum")))

Checking if a string is lower case

print("islower: " + str(lorem.islower()))

Checking if a string is numeric

print("isnumeric: " + str(lorem.isnumeric()))

Checking if a string contains a white space

print("isspace: " + str(lorem.isspace()))

Testing for string equality

lorem2 = "lorem ipsum"
if lorem == "lorem ipsum":
  print("The strings are equal")
else:
  print("The strings are not equal")

This check is quite simple, but somewhat incorrect as it is case-sensitive. If you want to compare two strings without case-sensitivity, the following is more suitable:

lorem2 = "lorem ipsum"
if lorem.lower() == lorem2.lower():
  print("The strings are equal")
else:
  print("The strings are not equal")

Checking if a string contains a certain substring

print("m" in lorem)
print("a" in lorem)

This will return true, if the string contains the substring in question.

Checking at which index a certain substring appears

print("lorem", lorem.find("lorem"))
print("rem", lorem.find("rem"))
print("ips", lorem.find("ips"))
print("abc", lorem.find("abc"))

This will return a number indicating where the substring in question occurs. If the number is -1, then the substring is not present.

Checking how often a substring appears in a string

The easiest and most common way to check that is by using count:

teststring = "abbaaaa"
print(teststring.count("aa"))

Note that count ignores overlapping occurences. Here, the number 2is printed.

Iterating through a string

i = 0
while i < len(lorem):
  print(lorem[i])
  i = i +1

Another way could be as follows:

for c in lorem:
  print(c)

This is a bit shorter and more pythonic.

Splitting a string

splitted = lorem.split(" ")
for word in splitted:
  print(word)

Here, the string will be splitted at each white space. You can use other separators as well.

Removing a character in a string

new_lorem = lorem.replace("m", "")

Inserting a character into a string

new_lorem = lorem[:5] + "-" + lorem[6:]

This will insert a dash after the fifth character.

Using the not operator with strings

name=""
if not name:
  print("the name is not set")
name="abc"
if not name:
  print("the name is not set")
else:
  print("now the name is set")

Further resources

Example code for the string operations above can be found here
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