Strings in python

One of the many basic data types of a programing language is the string data type, this post will be just a quick overview of strings in python. A string can often be considered a sequence of characters, so they are often used as a way to store text values, however they can also often be used to store an array of values like that of a list.

On top of the very basics of strings, there are also a number of string methods with the data type. So it would be a good idea to go over some of these methods that there are to work with when it comes to strings, such as uppercase, cont, find and so forth.

1 - basics of strings in python

Well I have to start somewhere when it comes to learning a thing or two about strings in python. In this section I will just be going over a few quick basic examples of strings. There is just creating a string literal value for starters, but then there are other basic things that I should have solid when it comes to learning about strings in a new language such as python. One thing that comes to mind with this is concatenation of strings, there is also the question of how to go about converting a string of a number to an actual number data type, and much more just when it comes to the basics. So lets get this part out of the way so i can move on to the good stuff.

1.1 - Basic string literal example

So maybe one of the first things I should learn when it comes to how to work with strings in a new programing environment is to learn how to create just a simple string literal value.

str='hello world'
print( type(str).__name__ ); # 'str'
print( str )                 # 'hello world'

1.2 - A string can be the result of an expression

On top of just being a simple string literal, a string can also be the result of an expression. When doing so it is called for to make sure that any value that is not a string is converted to a string. If I add a value that is a string, to a value that is not a string, I can end up with a type error.

def iNeedAbout(amount=3.5):
    return 'I need about $' + str(amount)
 
print(iNeedAbout())     # I need about $3.5
print(iNeedAbout(6.66)) # I need about $6.66

1.3 - Converting a string to an integer value

In javaScript when I add a string of a number such as 5 to a number such as 7 then the result is the string 57 rather than the number 12. If I want the number 12 rather than the string 57 then I will need to preform type conversion. In python if I attempt to just add a string and a number value together the result will be a type error. So when working out an expression where I might need to convert a string value of a number to an actual number data type then I have to always do type conversion.

One way to do type conversion of a string of a number to an actual number data type would be to use the int built in function.

str='42'
print( type(str).__name__ ) # str
print( str )                # 42
 
n=int(str)
print( type(n).__name__ )   # int
print( n )                  # 42

There are other built in functions such as the float function, but the basic idea is more or less the same. In any case to convert a string value to another value it will just require passing the string value to the appropriate built in function, or whatever method or function there is to preform the type conversion.

1.4 - Concatenate strings

Concatenating strings can work more or less the same way as I am used to coming from a javaScript background. However I will want to make sure that all the values are converted to strings when just adding them together first. Python will not do type conversion for me like in javaScript, not a big deal I just need to always use the str built in function for any and all values that might not be a string in most cases thus far.

# if two strings I can just add
a = 'hello'
b = 'world'
c = a + ' ' + b
print(c) # hello world
 
# if one value is not a string
# it must be turned into a string first
a = 42
b = 'foo'
try:
    c = a + ' ' + b
except TypeError:
    print('TypeError')
# TypeError
 
c = str(a) + ' ' + b
print(c)
# 42 foo

1.5 - I can loop over strings in python

A string can be looped over with a for loop in python.

str='12345'
for c in str:
    print( pow(2, int(c)), end=',' )
# 2,4,8,16,32,

2 - String Methods

Just like with strings in javaScript, and a number of other languages I am sure, there are are number of built in methods that can be called off of an instance of a string. Many of the usual suspects are there such as a split method that can be used to create a list of strings from a string. So then in this section I will be going over a few key methods such as split, fine, count, lower, and so forth.

2.1 - The split method

The split string method can be used to create a list iof strings from a string with a separator. There is however one major drawback with this method though which is that I can not give an empty string as a separator. So then the split method will fall short if I want to split a sing into a list of chars. However one work around would be to pass the string value to the list built in function.

str = '0,1,2,3,4,5'
l = str.split(',')
 
print(type(l).__name__) # list
print(l[3]) # 3
 
str = '012345'
# I can not give and empty string as a sep
# doing so will result in an error
try:
    l = str.split('')
except ValueError:
    print('ValueError')
 
# however there are a number of other ways to
# get that kind of list such as passing the string value
# to the list built in function
l = list(str);
print(type(l).__name__) # list
print(l[3]) # 3

2.2 - The count method

There is a count method that will return the number of times that a sub string happens in the given string that the method is called off of.

str='This is a sample text that contains text and also is text'
 
print(str.count('text')) # 3

3 - Conclusion

So far I have to say that learning python has been going pretty fast for me at least. However that might largely be because I have many years of experience working with javaScript, so much of this is just a question of how do I do x in python rather than javaScript. I am glad that I took the time to start learning another language, doing so has resulted in me having more appreciation for things that are more or less the same across languages. There are some differences between python and javaScript when it comes to strings, but there is only so much, so this was a pretty quick and painless process for me.

Well that is it for now when it comes to strings in python. I am still fairly new with python myself as of this writing so at some point in the future I will have to come back and edit this post as I start to pick pick up more when it comes to strings and python in general actually.