15-112 Fundamentals of Programming

# String Concatenation

print("Hello" + "World" + "!")  # prints HelloWorld!
print("Hello" "World" "!")      # prints HelloWorld!
s = "Hello"
print(s + "World" + "!")        # prints HelloWorld!
print(s "World" "!")            # Error

print("hi"*3)                   # prints hihihi
print(3*"hi")                   # prints hihihi
print(2*"hi"*2)                 # prints hihihihi


# String Indexing

s = "Go Tartans!"

print(s[0])                # prints G
print(s[5], s[10], s[3])   # prints r ! T

print(s[-1])               # prints !
print(len(s))              # prints 11
print("Yabadabaduuu!"[5])  # prints a
print(s[len(s)])           # Crashes: index error


# String Slicing

print(s[3:len(s)])         # prints Tartans!
print(s[0:len(s)])         # prints Go Tartans!
print(s[3:])               # prints Tartans!
print(s[:1])               # prints G
print(s[:])                # prints Go Tartans!

print(s[0:len(s):2])       # prints G atn!
print(s[::])               # prints Go Tartans!
print(s[len(s)-1:0:-1])    # prints !snatraT o
print(s[len(s)-1:-1:-1])   # prints nothing (range is empty)
print(s[::-1])             # prints !snatraT oG 


# Strings are immutable

s[3] = "t"                 # error

s += " haha"               # creates a new string in memory
print(s)                   # prints Go Tartans! haha

s = s[:3] + "t" + s[4:]    # effectively s[3] = "t"
print(s)                   # prints Go tartans! haha

# Looping over a string with an index:
s = "hello"
for i in range(len(s)):
    print(i, s[i])

# Looping over a string without an index:
for c in s:
    print(c)

def isPalindrome(s):
    mid = len(s)//2
    for i in range(mid):
        if (s[i] != s[len(s)-1-i]): return False
    return True