String manipulation in Python 3.

Use input() function
The input data is string, needed to be converted to other data types if necessary, for example, num = int(str)

name = input('Enter a name: ')
print(name)

# Tracy

Index of Strings

fruit = 'banana'
print(fruit[0]) # output: b. Pronouncation: fruit sub 0
x = 3
w = fruit[x - 1]
print(w) # output: n

Get the Length of a String

len() function

1	print(len(fruit)) # output: 6

Looping through Strings

# while loop
index = 0
while index < len(fruit):
    letter = fruit[index]
    print(index, letter)
    index += 1
print('Done')
# for loop
for letter in fruit:
    print(letter)
print('Done')

Slicing Strings

Use the colon operator, ‘start’:’end’
The first number is including, the second number is excluding.
If the second number is beyond the end of this string, it gets the rest of the string.
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s = 'Tracy Yang'
print(s[0:4]) # output: Trac
print(s[4:20]) # output: y Yang
No first number: get the substring from 0 (including) to the second number (excluding)
No second number: get the substring from the first number (including) to the end
Just colon operator: get the whole string

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print(s[:2]) #Tr
print(s[8:]) #ng
print(s[:]) #Tracy Yang

String Concatenation

a = 'Hello'
b = a + 'There'
print(b) # output: HelloThere
c = a + ' ' + 'There'
print(c) # output: Hello There

Check if one string ‘is’ in another string

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print('n' in fruit) #True
print('m' in fruit) #False
print('nan' in fruit) #True

Searching a String

string.find():

Returns the index of the first occurrence
Returns -1 if not found

na = fruit.find('na')
# at index of 2
print(na) # output: 2 
ma = fruit.find('ma')
# not exist
print(ma) # output: -1

Make Uppercase

string.upper(): returns a new string, the old one doesn’t change.

1 2	greet = 'Hello Tracy' print(greet.upper()) # output: HELLO TRACY

Search and Replace

string.replace()

Replace a string with another, the old string doesn’t change.
It replaces all occurrence in the old string.
If the target substring is not found, then the original string is returned.

# 1.
greet2 = greet.replace('Tracy', 'Lucy')
print(greet2) # output: Hello Lucy
print(greet) # output: Hello Tracy
# 2.
greet3 = greet.replace('l', '!')
print(greet3) # output: He!!o Tracy
# 3.
greet4 = greet.replace('X', 'a')
print(greet4, 123) # output: Hello Tracy 123

Stripping Whitespace

string.lstrip() and string.rstrip(): remove whitespace at left or right
string.strip(): remove whitespace at both sides

whiteSpace = '    Hello There   '
print(whiteSpace.lstrip()) # output: 'Hello There   '
print(whiteSpace.rstrip()) # output: '    Hello There'
print(whiteSpace.strip()) # output: 'Hello There;

Prefixes

string.startswith(str): return True if the string starts with the input, otherwise False.

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line = 'Please sit down.'
print(line.startswith('Please')) # output: True
print(line.startswith('p')) # output: False

python course 2 week 1 Index of Strings Get the Length of a String Looping through Strings Slicing Strings String Concatenation Check if one string ‘is’ in another string Searching a String Make Uppercase Search and Replace Stripping Whitespace Prefixes