03_string_operations.md

String Operations

city = 'San Francisco'
print(len(city))

print(city.split())

print(city.upper())

city[0]

city[-1]

city[0:3]

city[4:]

Escaping characters

Certain characters are special since they are by Python language itself. For example, the quote character ' is used to define a string. What do you do if your string contains a quote character?

In Python strings, the backslash \ is a special character, also called the escape character. Prefixing any character with a backslash makes it an ordinary character. (Hint: Prefixing a backslash with a backshalsh makes it ordinary too!)

It is also used for representing certain whitespace characters, \n is a newline, \t is a tab etc.

Remove the # from the cell below and run it.

# my_string = 'It's a beautiful day!'

We can fix the error by espacing the single quote within the string.

my_string = 'It\'s a beautiful day!'
print(my_string)

Alternatively, you can also use double-quotes if your string contains a single-quote.

my_string = "It's a beautiful day!"

What if our string contains both single and double quotes?

We can use triple-quotes! Enclosing the string in triple quotes ensures both single and double quotes are treated correctly.

latitude = '''37° 46' 26.2992" N'''
longitude = '''122° 25' 52.6692" W'''
print(latitude, longitude)

Backslashes pose another problem when dealing with Windows paths

#path = 'C:\Users\ujaval'
#print(path)

Prefixing a string with r makes is a Raw string. Which doesn't interpret backslash as a special character

path = r'C:\Users\ujaval'
print(path)

Printing Strings

Modern way of creating strings from variables is using the format() method

city = 'San Fransico'
population = 881549
output = 'Population of {} is {}.'.format(city, population)
print(output)

You can also use the format method to control the precision of the numbers

latitude = 37.7749
longitude = -122.4194

coordinates = '{:.2f},{:.2f}'.format(latitude, longitude)
print(coordinates)

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Exercise

Use the string slicing to extract and print the degrees, minutes and second parts of the string below. The output should be as follows

37
46
26.2992

latitude = '''37° 46' 26.2992"'''