Concatenation

Concatenation means joining strings. print(x + y) will concatenate x and y together and print the resulting string, e.g., "Hello" + "World" = "HelloWorld". print(x, y) will print x and y as separate values with a space in between, e.g., "Hello", "World" = "Hello World". The former wouldn't work with a string and an integer, but the latter would. However, we could convert an integer to a string and then concatenate: print(x + str(y)).

# Checking if a string contains a specified substring
print("y" in "Python")
print("y" not in "Python")                                        
                                    

len()

# A number of characters in a string (its length)
x = "Python"
print(len(x))
                                    

String indexing

A string index is the position number used to access or reference a specific substring within a string, starting from 0.

x = "Python"
print(x[0]) # the first character - "P"
print(x[2]) # the third character - "t"
print(x[-1]) # the last character - "n"
print(x[1:3]) # from the 2nd character (included) to the 4th (excluded) - "yt"
print(x[::-1]) # reversed order - "nohtyP"
print(x[::2]) # every 2nd character - "Pto"
print(x[1::2]) # from the 2nd character to the end, every 2nd character - "yhn"
print(x[::-2]) # every 2nd character counting from the back - "nhy"
print(x[2:]) # from the 3rd character (included) to the end - "thon"
print(x[:2]) # from the start to the 3rd character (excluded) - "Py"
print(x[-3:-1]) # from the 3rd last (included) to the last character (excluded) - "ho"
                                    

Iterating a string

# Getting access to every single string character independently
x = "Python"
for y in x:
    print(y)
                                    

replace()

# Replacing a fragment of a string
x = "Python"
print(x.replace("Py", "AA"))
                                    

startswith() and endswith()

text = "Python"
# Checking if a string is at the beginning of a text
if text.startswith("Py"):
    print("True")
# Checking if a string is at the end of a text
if text.endswith("on"):
    print("True")
                                    

find() / index()

# Finding the position of the first occurrence of a substring in a string (the index of the substring's first letter). If there are more than one - the index of the first one encountered.
x = "Python"
print(x.find("n"))
print(x.index("n"))
                                    

count()

# Counting the number of times a substring occurs in a string
x = "Python"
print(x.count("n")
                                    

Lowercase and uppercase

x = "Python"
# Lowercase to uppercase
print(x.upper())
# Uppercase to lowercase
print(x.lower())
# Lowercase to uppercase, uppercase to lowercase
print(x.swapcase())
                                    

x = "PYTHON"
y = "python"
# Checking if a string is in uppercase
if x.isupper():
    print("True")
# Checking if a string is in lowercase
if y.islower():
    print("True")
                                    

A few more methods with the is prefix:

• The isdecimal() method returns True if the string consists only of numeric characters (0–9) and is not empty.
• The isdigit() method returns True if the string consists of numeric characters or other numeric symbols (e.g., subscripts) and is not empty.
• The isalpha() method returns True if the string consists only of letters and is not empty.
• The isalnum() method returns True if the string consists only of letters and numbers and is not empty.
• The isspace() method returns True if the string consists only of spaces, tabs, and new lines and is not empty.
• The istitle() method returns True if the string consists only of words beginning with an uppercase letter followed by lowercase letters.

Margins

x = "Python"
print(x.center(20)) # margins from both sides
print(x.rjust(20)) # margin from the left
print(x.ljust(20)) # margin from the right
                                    

Whitespace characters

x = "    Python    "
print(x.strip()) # deleting whitespace characters
print(x.rstrip()) # deleting whitespace characters from the right
print(x.lstrip()) # deleting whitespace characters from the left
                                    

Unicode

print(ord("A")) # coding Unicode characters
print(chr(65)) # decoding Unicode characters
                                    

In Python, we can compare two strings using the same signs as with numbers. A string can be "lesser" or "greater" than another string based on two factors: its length and the alphabetical order of compared characters. Check out how this works in your editor.