Ⅱ. Basic data types
#type()

1. Boolean （布尔值）

Ture
False

2. Integer（整型）

3. Float （浮点数）
ⅰ) 取整
a.四舍五入

round()

eg.
b.向上/下取整

math.ceil()
math.floor()

eg.

ⅱ)Convert between int and float

int()
float()

4. String（字符串）
immutable  ordered

ⅰ) Basics
a.

 +.*

b.

in
not in

ⅱ) Built-in functions
a.

len()

b.
ⅲ) Index

str[]

ⅳ) Slicing

string_x [start: stop: step]

a) positions are inclusive at the start, but exclusive at the stop.
b) step can be specified to specify steps in slicing; the default value of step is 1.

ⅴ) String methods
# All string methods returns new values. They do not change the original string.
a) lower() ,upper()

string.lower() 
string.upper()

b> replace()

string.replace(oldvalue, newvalue, count)

c) count()

string.count(value, start, end)

d) find()

string.find(value, start, end)

e) split()

string.split(separator, maxsplit)

f) startswith(), endswith()

string.startswith(value, start, end) 
string.endswith(value, start, end)

g) strip()

string.strip(characters)

ⅵ) Conversion between data types

str()
int()
float()