• 들어가기 전에
  : 해당 강좌는 MIT 의 OpenCourseWare 수업을 듣고 내용을 정리한 것이다.
  : 강좌명은 Introduction To Computer Science And Programming In Python, 6.0001 이며 링크는 다음과 같다.
  https://ocw.mit.edu/courses/6-0001-introduction-to-computer-science-and-programming-in-python-fall-2016/video_galleries/lecture-videos/

배울 내용

1. String manipulation

1. String manipulation

Strings

• Think of as a sequence of case sensitive characters

• can compare strings with ==, >, <, etc

• len() : retrieve the length of the string in the parantheses

  s = "abc"
  print(len(s)) # 3

Indexing

• Use square brackets to perform indexing into a string

# s =     "a  b  c"
# index :  0  1  2
# index : -3 -2 -1

s = "abc"
print(s[0]) # a
print(s[1]) # b
print(s[2]) # c
# print(s[3]) # trying to index out of bounds, error
print(s[-1]) # c
print(s[-2]) # b
print(s[-3]) # a

Slicing

• Can slice strings using [start : stop : step]
• if give two numbers, [start : stop], step = 1 by default
• you can also omit numbers and leave just colons

s = "abcdefgh"
print(s[3 : 6]) # "def"
print(s[3 : 6 :2]) # "df"
print(s[::]) # "abcdefgh"
print(s[::-1]) "hgfedcba"
print(s[4:1:-2]) "ec"

Mutablility

• Strings are immutable
  : An actual string object, onece it's created, cannot be modified

s = "hello"

# s[0] = 'y' # gives an error
s = 'y' + s[1:len(s)] # allowed, s bound to new object
print(s) # yello

Strings and Loops

• for loops
  : range is a way to iterate over numbers, but for loop can iterate over any set of values, not just numbers
• Compare two loops
  : Bottom one is more "pythonic"

s = "abcdefgh"
for index in range(len(s)) : 
  if s[index] == 'i' or s[index] == 'u' : 
    print("There is an i or u")

s = "abcdefgh"
for char in s : 
  if char == 'i' or char == 'u' : 
    print("There is an i or u")