Master Python Data Types, Operators, and String Formatting: A Complete Guide

Python Data Types

Number (数字)

String (字符串)

List (列表)

Dictionary (字典)

Tuple (元组)

Set (集合)

Numbers, strings, and tuples are immutable; lists and dictionaries are mutable. Reassigning an immutable variable actually creates a new object and redirects the name to it.

Numbers

int: integer

<code>1. 正负数
2. 十六进制 (0x or 0X, e.g., 0xff)
3. 八进制 (0o or 0O, e.g., 0o632457)
4. 二进制 (0b or 0B, e.g., 0b101100)</code>

fraction: 分数

float: 浮点数

complex: 复数

bool: 布尔型 (True or False)

Base Conversion

Integer to other bases

Use

bin(i)

,

oct(i)

,

hex(i)

to convert decimal to binary, octal, or hexadecimal.

<code>>> s=10
>>> bin(s)
'0b1010'
>>> oct(s)
'0o12'
>>> hex(s)
'0xa'</code>

Convert non‑decimal strings to integers with

int(str, base)

where

base

can be 2, 8, 16, up to 36.

<code>>> int('0b10010', 2)
18
>>> int('0o52415', 8)
21773
>>> int('0x134ab', 16)
79019
>>> int('s', 32)
28
>>> int('yz', 36)
1259</code>

Hexadecimal can also be converted to binary or octal, and vice‑versa.

<code>>> hex(0b1001)
'0x9'
>>> oct(0b101)
'0o5'
>>> bin(0xff)
'0b11111111'</code>

Operators

Arithmetic:

+, -, *, /, //, %, **

Comparison:

==, !=, >, <, <=, >=

Assignment:

=, +=, -=, *=, /=, %=, //=, **=

Bitwise:

&, |, ^, ~, <<, >>

Logical:

and, or, not

Membership:

in, not in

Identity:

is, is not

<code>>> a=12
>>> f=~a
>>> f
-13
>>> bin(a)
'0b1100'
>>> bin(a&lt;&lt;1)
'0b11000'
>>> bin(a&gt;&gt;1)
'0b110'
>>> lst=[1,2,3,4,5]
>>> a=3
>>> a in lst
True
>>> a not in lst
False
>>> b=a[:]
>>> b is a
False</code>

Operator Precedence

** (exponentiation) – highest

~, +, - (unary)

*, /, //, %

+, -

<<, >>

&

^, |

<=, >=, <, >

==, !=

=, +=, -=, *=, /=, //=, %=, **=

Math Functions

power: same as

**

<code>>> pow(2,3)
8</code>

sqrt: square root

<code>>> import math
>>> math.sqrt(4)
2.0</code>

max, min: maximum and minimum

<code>>> max(2,3,4,5,1,9,6)
9
>>> min(2,3,4,5,1,9,6)
1</code>

abs, math.fabs: absolute value (float version)

round: round to nearest, ties to even

math.ceil / math.floor: ceiling and floor

cmp (Python 2): returns -1, 0, 1 for comparison

random module:

random.random()

,

random.choice()

,

random.sample()

,

random.shuffle()

,

random.getrandbits()

math.modf: separate fractional and integer parts

math.log, math.log2, math.log10: logarithms with optional base

Decimal module for precise decimal arithmetic

Strings

Python 2 uses ASCII by default; Unicode strings are prefixed with

u

. Python 3 uses Unicode.

String Literals

Single quotes:

'str'

Double quotes:

"str"

Triple quotes for multi‑line strings

Escape characters:

"\t"

,

"\n"

Raw strings:

r"C:\path\file"

String Operations

Concatenation

<code>>> 'abc' + 'def'
'abcdef'
>>> 'hello' * 5
'hellohellohellohellohello'</code>

Indexing & Slicing

<code>>> text = 'this_is_str'
>>> text[0:4]
'this'
>>> text[5:7]
'is'
>>> text[:4]
'this'
>>> text[-3:]
'str'
>>> text[::2]
'ti_ssr'
>>> text[8:1:-2]
'ss_i'</code>

Encoding Conversion

<code>>> ord('d')
100
>>> chr(99)
'c'
>>> ord('王')
29579
>>> chr(29579)
'王'</code>

Case Conversion (manual)

<code>>> Text = ''
>>> text = "aSdFgHjK"
>>> for i in text:
...     i_code = ord(i)
...     if 97 <= i_code <= 122:
...         Text += chr(i_code-32)
...     else:
...         Text += i
>>> Text
'ASDFGHJK'</code>

Case Conversion (built‑in methods)

capitalize()

: first character uppercase

title()

: first character of each word uppercase

upper()

,

lower()

,

swapcase()

Alignment and Padding

<code>>> 'hello'.center(11)
'   helloo  '
>>> 'hello'.ljust(11, '_')
'helloo_____' 
>>> 'hello'.rjust(11, '_')
'_____hello'</code>

Whitespace Handling

<code>>> 'hello\tworld'.expandtabs(9)
'hello    world'
>>> 'sad'.zfill(10)
'0000000sad'</code>

Trimming

<code>>> '  hello world  '.strip()
'hello world'
>>> 'hello,world'.strip('h')
'ello,world'</code>

Searching

startswith()

/

endswith()

count()

find()

/

rfind()

index()

/

rindex()

replace(old, new, count)

Character Classification

isalpha()

,

isdigit()

,

isalnum()

,

islower()

,

isupper()

,

isspace()

,

istitle()

,

isdecimal()

,

isnumeric()

,

isidentifier()

,

isprintable()

Splitting

<code>>> 'asd,fgh,jkl'.split(',')
['asd', 'fgh', 'jkl']
>>> 'asd,fgh,jkl'.rsplit(',', 1)
['asd,fgh', 'jkl']
>>> 'asd\nfgh\njkl'.splitlines()
['asd', 'fgh', 'jkl']
>>> 'http://www.baidu.com'.partition('://')
('http', '://', 'www.baidu.com')</code>

Joining

<code>>> '-'.join('asdfg')
'a-s-d-f-g'</code>

String Formatting

Three common methods:

Percent‑style (

%

)

str.format()

f‑strings

Percent‑style

<code>>> "%s|%r|%c" % ("this is str", "this is repr", "C")
"this is str|'this is repr'|C"
>>> "%d|%o|%x|%X|" % (3, 12, 13, 14)
'3|14|d|E|'
>>> "%+10.2f" % 3.1
'     +3.10'
>>> "%#8x" % 10
'    0xa'</code>

str.format()

<code>>> "{0}'s password is {1}".format('wanger', 123456)
"wanger's password is 123456"
>>> "{1}'s password is {0}".format(123456, 'wanger')
"wanger's password is 123456"
>>> "{:.4f}".format(3.1415926)
'3.1416'
>>> "{0:b},{0:o},{0:x}".format(10)
'1010,12,a'
>>> "{0:#b},{0:#o},{0:#x}".format(10)
'0b1010,0o12,0xa'
>>> "{:,}".format(100000000000)
'100,000,000,000'</code>

f‑strings

<code>>> name = 'wanger'
>>> age = 25
>>> f"Hello, I'm {name}, age {age}"
"Hello, I'm wanger, age 25"
>>> f"{2*3}"
'6'
>>> f"{name.lower()} is funny"
"wanger is funny"
>>> comedian = {'name':'wanger','age':25}
>>> f"The comedian is {comedian['name']}, aged {comedian['age']}."
"The comedian is wanger, aged 25."
</code>

Practical Use Cases

Splitting with multiple delimiters using

re.split()

:

<code>>> import re
>>> re.split(r'[;,\s]\s*', 'asd,dfg;zxc ert  uio')
['asd', 'dfg', 'zxc', 'ert', 'uio']</code>

Checking prefixes/suffixes:

<code>>> url = 'http://www.baidu.com'
>>> url.startswith(('http://', 'ftp://'))
True
>>> filename = 'resource.txt'
>>> filename.endswith('txt')
True</code>

Shell‑style pattern matching with

fnmatch

:

<code>>> from fnmatch import fnmatch, fnmatchcase
>>> fnmatch('log.txt', '*.txt')
True
>>> fnmatchcase('log.TXT', '*.txt')
False
>>> fnmatchcase('log.TXT', '*.TXT')
True</code>

Regular‑expression date conversion:

<code>>> import re
>>> date = 'today is 13/12/2018'
>>> re.sub(r'(\d+)/(\d+)/(\d+)', r'\3-\2-\1', date)
'today is 2018-12-13'
>>> pattern = re.compile(r'(\d+)/(\d+)/(\d+)')
>>> pattern.sub(r'\3-\2-\1', date)
'today is 2018-12-13'
>>> pattern.subn(r'\3-\2-\1', 'yestory is 12/12/2018,today is 13/12/2018')
('yestory is 2018-12-12,today is 2018-12-13', 2)</code>

Case‑insensitive search and replace:

<code>>> import re
>>> re.findall('replace', 'Replace,replace,REPLACE')
['replace']
>>> re.findall('replace', 'Replace,replace,REPLACE', flags=re.IGNORECASE)
['Replace', 'replace', 'REPLACE']
>>> re.sub('replace', 'WORD', 'Replace is the same as REPLACE', flags=re.IGNORECASE)
'WORD is the same as WORD'</code>