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Python Strings
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This was referenced from w3schools.com.
Strings
Strings in python are surrounded by either single quotation marks, or double
quotation marks.
'hello' is the same as "hello".
You can display a string literal with the print() function:
quotation marks.
'hello' is the same as "hello".
You can display a string literal with the print() function:
print("Hello")
print('Hello')
print('Hello')
Assign String to a Variable
Assigning a string to a variable is done with the variable name followed by an
equal sign and the string:
equal sign and the string:
a = "Hello"
print(a)
print(a)
Multiline Strings
You can assign a multiline string to a variable by using three quotes:
You can use three double quotes:
You can use three double quotes:
a = """Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua."""
print(a)
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua."""
print(a)
Or three single quotes:
a = '''Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua.'''
print(a)
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua.'''
print(a)
Note: in the result, the line breaks are inserted at the same position as in the
code.
code.
Strings are Arrays
Like many other popular programming languages, strings in Python are arrays
of bytes representing unicode characters.
However, Python does not have a character data type, a single character is
simply a string with a length of 1.
Square brackets can be used to access elements of the string.
Get the character at position 1 (remember that the first character has the
position 0):
of bytes representing unicode characters.
However, Python does not have a character data type, a single character is
simply a string with a length of 1.
Square brackets can be used to access elements of the string.
Get the character at position 1 (remember that the first character has the
position 0):
a = "Hello, World!"
print(a[1])
print(a[1])
Looping Through a String
Since strings are arrays, we can loop through the characters in a string, with a
for loop.
Loop through the letters in the word "banana":
for loop.
Loop through the letters in the word "banana":
for x in "banana":
print(x)
print(x)
String Length
To get the length of a string, use the len() function.
The len() function returns the length of a string:
The len() function returns the length of a string:
a = "Hello, World!"
print(len(a))
print(len(a))
Check String
To check if a certain phrase or character is present in a string, we can use the
keyword in.
Check if "free" is present in the following text:
keyword in.
Check if "free" is present in the following text:
txt = "The best things in life are free!"
print("free" in txt)
print("free" in txt)
Use it in an if statement:
Print only if "free" is present:
Print only if "free" is present:
txt = "The best things in life are free!"
if "free" in txt:
print("Yes, 'free' is present.")
if "free" in txt:
print("Yes, 'free' is present.")
Check if NOT
To check if a certain phrase or character is NOT present in a string, we can use
the keyword not in.
Check if "expensive" is NOT present in the following text:
the keyword not in.
Check if "expensive" is NOT present in the following text:
txt = "The best things in life are free!"
print("expensive" not in txt)
print("expensive" not in txt)
Use it in an if statement:
print only if "expensive" is NOT present:
print only if "expensive" is NOT present:
txt = "The best things in life are free!"
if "expensive" not in txt:
print("No, 'expensive' is NOT present.")
if "expensive" not in txt:
print("No, 'expensive' is NOT present.")
Slicing Strings
You can return a range of characters by using the slice syntax.
Specify the start index and the end index, separated by a colon, to return a part
of the string.
Get the characters from position 2 to position 5 (not included):
Specify the start index and the end index, separated by a colon, to return a part
of the string.
Get the characters from position 2 to position 5 (not included):
b = "Hello, World!"
print(b[2:5])
print(b[2:5])
Note: The first character has index 0.
Slice From the Start
By leaving out the start index, the range will start at the first character:
Get the characters from the start to position 5 (not included):
Get the characters from the start to position 5 (not included):
b = "Hello, World!"
print(b[:5])
print(b[:5])
Slice To the End
By leaving out the end index, the range will go to the end:
Get the characters from position 2, and all the way to the end:
Get the characters from position 2, and all the way to the end:
b = "Hello, World!"
print(b[2:])
print(b[2:])
Negative Indexing
Use negative indexes to start the slice from the end of the string:
Get the characters:
From: "o" in "World!" (position -5)
To, but not included: "d" in "World!" (position -2):
Get the characters:
From: "o" in "World!" (position -5)
To, but not included: "d" in "World!" (position -2):
b = "Hello, World!"
print(b[-5:-2])
print(b[-5:-2])
Modify Strings
Python has a set of built-in methods that you can use on strings.
Upper Case
The upper() method returns the string in upper case:
a = "Hello, World!"
print(a.upper())
print(a.upper())
Lower Case
The lower() method returns the string in lower case:
a = "Hello, World!"
print(a.lower())
print(a.lower())
Remove Whitespace
Whitespace is the space before and/or after the actual text, and very often you
want to remove this space.
The strip() method removes any whitespace from the beginning or the end:
want to remove this space.
The strip() method removes any whitespace from the beginning or the end:
a = " Hello, World! "
print(a.strip()) # returns "Hello, World!"
print(a.strip()) # returns "Hello, World!"
Replace String
The replace() method replaces a string with another string:
a = "Hello, World!"
print(a.replace("H", "J"))
print(a.replace("H", "J"))
Split String
The split() method returns a list where the text between the specified
separator becomes the list items.
The split() method splits the string into substrings if it finds instances of the
separator:
separator becomes the list items.
The split() method splits the string into substrings if it finds instances of the
separator:
a = "Hello, World!"
print(a.split(",")) # returns ['Hello', ' World!']
print(a.split(",")) # returns ['Hello', ' World!']
String Concatenation
To concatenate, or combine, two strings you can use the + operator.
Merge variable a with variable b into variable c:
Merge variable a with variable b into variable c:
a = "Hello"
b = "World"
c = a + b
print(c)
b = "World"
c = a + b
print(c)
To add a space between them, add a " ":
a = "Hello"
b = "World"
c = a + " " + b
print(c)
b = "World"
c = a + " " + b
print(c)
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