Python Strings¶

Strings are just a variable that is assigned a series of characters between a single, double or tripple quotes.

Combine Strings¶

You can combine strings using the + sign

In [31]:

print("Python" + "Programming")

print("Python" + "Programming")

PythonProgramming

Length of a String¶

You can check how long a string is (how many characters it has including spaces) using the len() method:

In [32]:

word = "python"
print("Length of string: ", len(word))

word = "python" print("Length of string: ", len(word))

Length of string:  6

Extracting specific characters¶

You can get specific characters from a string using the bracket notation by using the index:

[0] [1] [2] [3] [4] [5]
p - y - t - h - o - n

In [33]:

print("The first character in the word is: ", word[0])

print("The first character in the word is: ", word[0])

The first character in the word is:  p

You can ge the last character of a string by using the same bracket notation but with -1 which means the last character from the end.

In [34]:

print("The last character in the word is: ", word[-1])

print("The last character in the word is: ", word[-1])

The last character in the word is:  n

To get the first three characters of a string you would use the splice notation:

In [35]:

print("The first three characters in the word are: ", word[0:3])

print("The first three characters in the word are: ", word[0:3])

The first three characters in the word are:  pyt

Replacing string values¶

You cannot normally assign a different character in a string. For example if we wanted to replace the 'p' in python with an 's', we would get an error if we tried this:

In [36]:

word[0] = 's'

word[0] = 's'

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[36], line 1
----> 1 word[0] = 's'

TypeError: 'str' object does not support item assignment

However, we can replace a character using the replace method:

In [37]:

word = word.replace("p", "s")
print(word)

word = word.replace("p", "s") print(word)

sython

You can also slice the string and then replace it with a diffrent part of a string:

In [38]:

word = word[0:3] + "something" + word[3:]
print(word)

word = word[0:3] + "something" + word[3:] print(word)

sytsomethinghon

Checking Strings¶

We can check if a string exists within a string:

In [39]:

languages = "python and c"
print("python" in languages)

languages = "python and c" print("python" in languages)

True

In [40]:

print("java" in languages)

print("java" in languages)

False

You can find the first index of a string if a string matches:

In [44]:

print("Index location of the word and starts at index: ", languages.find('and'))

print("Index location of the word and starts at index: ", languages.find('and'))

Index location of the word and starts at index:  7

You can check if a all characters in a string are alphabet characters using isalpha() (not including spaces):

In [63]:

"word".isalpha()

"word".isalpha()

Out[63]:

True

Check if all characters are numerical:

In [64]:

"123".isnumeric()

"123".isnumeric()

Out[64]:

True

Or even both

In [65]:

"word123".isalnum()

"word123".isalnum()

Out[65]:

True

Removing white spaces (regular spaces)¶

You can remove spaces from the left and right side of a string using the strip() method:

In [54]:

"               Lots of spaces            ".strip()

" Lots of spaces ".strip()

Out[54]:

'Lots of spaces'

Only the left side:

In [53]:

"               Lots of spaces            ".lstrip()

" Lots of spaces ".lstrip()

Out[53]:

'Lots of spaces            '

Only the right side:

In [52]:

"               Lots of spaces            ".rstrip()

" Lots of spaces ".rstrip()

Out[52]:

'               Lots of spaces'

Converting a List <-> String¶

If you want to convert a list into a string separated by spaces, you would do:

In [51]:

" ".join(["List", "of", "words"])

" ".join(["List", "of", "words"])

Out[51]:

'List of words'

and a string into a list based on how the words are separated:

In [57]:

"List of words".split(" ")

"List of words".split(" ")

Out[57]:

['List', 'of', 'words']

Formating Strings¶

You can format the output of your strings using f-strings:

In [58]:

version = 3
f"You are using Python {version}"

version = 3 f"You are using Python {version}"

Out[58]:

'You are using Python 3'

Yyou can make characters upper case or lower case:

In [59]:

"Some words".lower()

"Some words".lower()

Out[59]:

'some words'

In [61]:

"Some words".upper()

"Some words".upper()

Out[61]:

'SOME WORDS'

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