[Python tutorial] 5. Data type - Strings

Strings

Assign String to a Variable

a = "Hello"

파이썬 문자열은 변경 불가

a = 'Python'
a[0] = 'J' # error

Multiline Strings

a = """Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua."""
b = '''Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua.'''
# """string""", '''string''' 동일

'End of line' 자동 삽입 방지하려면 \ 사용

print("""\
Usage: thingy [OPTIONS]
     -h                        Display this usage message
     -H hostname               Hostname to connect to
""")

Strings are Arrays

a = "Hello, World!"
print(a[1]) # e

Looping Through a String

for x in "banana":
  print(x)

b
a
n
a
n
a

String Length: len()

a = "Hello, World!"
print(len(a))    # 13

Check String: keyword in

문자열이나 문자가 있는지 확인, True/False

txt = "The best things in life are free!"
print("free" in txt)    # True

txt = "The best things in life are free!"
if "free" in txt:    # True
  print("Yes, 'free' is present.")

Check if NOT: not in

txt = "The best things in life are free!"
print("expensive" not in txt)    # True

txt = "The best things in life are free!"
if "expensive" not in txt:    # True
  print("No, 'expensive' is NOT present.")

Slicing

b = "Hello, World!"

# slicing
print(b[2:5])    #llo
# 5는 제외(2-4 포함), 첫 글자의 인덱스는 0

# Slice From the Start
print(b[:5])    # Hello

# Slice To the End
print(b[2:])    # llo, World!

# Negative Indexing
print(b[-5:-2])    # orl
# -는 0에서 시작하지 않고 -1부터 시작

Modify Strings

a = "Hello, World!"
b = "  Hello, World!  "

# Upper Case: upper()
print(a.upper())    # HELLO, WORLD!

# Lower Case: lower()
print(a.lower())    # hello, world!

# Remove Whitespace: strip()
print(b.strip())    # Hello, World!

# Replace String: replace()
print(a.replace("H", "J"))    # Jello, World!

# Split String: split()
print(a.split(",")) # ['Hello', ' World!']

String Concatenation

+

a = "Hello"
b = "World"
c = a + " " + b
print(c)    # Hello World

*

3* 'un' + 'ium'
# 'unununium'

Escape Characters

txt = "We are the so-called \"Vikings\" from the north."
print(txt)
# We are the so-called "Vikings" from the north.

Code	Result
'	Single Quote
\\	Backslash
\n	New Line
\r	Carriage Return
\t	Tab
\b	Backspace
\f	Form Feed
\ooo	Octal value
\xhh	Hex value

Raw string, r

\등의 특수문자의 이스케이프를 방지
윈도우에서 \ 사용으로 필수, 맥은 / 사용하므로 필수 사용 아님

print('C:\some\name') # \n: new line
print(r'C:\some\name')

String format: format(), {}

age = 36
txt = "My name is John, and I am {}"
print(txt.format(age))    # My name is John, and I am 36

quantity = 3
itemno = 567
price = 49.1
myorder = "I want {} pieces of item {} for {} dollars."
print(myorder.format(quantity, itemno, price))
# I want 3 pieces of item 567 for 49.1 dollars.

Index number & number format

quantity = 3
itemno = 567
price = 49.95
myorder = "I want to pay {2:.2f} dollars for {0} pieces of item {1}." # index numbers
print(myorder.format(quantity, itemno, price))
# I want to pay 49.10 dollars for 3 pieces of item 567.

Named Indexes

myorder = "I have a {carname}, it is a {model}."
print(myorder.format(carname = "Ford", model = "Mustang"))

String methods

String Methods Reference

기타 참고자료

Text Sequence Type — str
String Methods
Formatted string literals
Format String Syntax
printf-style String Formatting