[!NOTE|label:references:]

pad

[!NOTE|label:sample variables]

days: list[str] = [ 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday' ]
pad: int = max([ len(i) for i in days ])

left

print( '\n' + ' left pad '.center(80, '-') )
for day in days: print( f"{day.title().ljust(pad, ' ')} -> {type(day)}" )
# ----------------------------------- left pad -----------------------------------
# Monday    -> <class 'str'>
# Tuesday   -> <class 'str'>
# Wednesday -> <class 'str'>
# Thursday  -> <class 'str'>
# Friday    -> <class 'str'>
# Saturday  -> <class 'str'>
# Sunday    -> <class 'str'>

print( ' pythonic '.center(50, '~') )
for day in days: print( f"{day.title():<{pad}} -> {type(day).__name__}" )
# ~~~~~~~~~~~~~~~~~~~~ pythonic ~~~~~~~~~~~~~~~~~~~~
# Monday    -> str
# Tuesday   -> str
# Wednesday -> str
# Thursday  -> str
# Friday    -> str
# Saturday  -> str
# Sunday    -> str

print( '\n' + ' right pad '.center(80, '-') )
for day in days: print( f"{day.upper().rjust(pad, ' ')} -> {type(day)}" )
# ---------------------------------- right pad -----------------------------------
#    MONDAY -> <class 'str'>
#   TUESDAY -> <class 'str'>
# WEDNESDAY -> <class 'str'>
#  THURSDAY -> <class 'str'>
#    FRIDAY -> <class 'str'>
#  SATURDAY -> <class 'str'>
#    SUNDAY -> <class 'str'>

print( ' pythonic '.center(50, '~') )
for day in days: print( f"{day.upper():>{pad}} -> {type(day).__name__}" )
# ~~~~~~~~~~~~~~~~~~~~ pythonic ~~~~~~~~~~~~~~~~~~~~
#    MONDAY -> str
#   TUESDAY -> str
# WEDNESDAY -> str
#  THURSDAY -> str
#    FRIDAY -> str
#  SATURDAY -> str
#    SUNDAY -> str

center

print( '\n' + ' center '.center(80, '-') )
for day in days: print( f" {day} ".center(20, '.') )
# ------------------------------------ center ------------------------------------
# ...... monday ......
# ..... tuesday ......
# .... wednesday .....
# ..... thursday .....
# ...... friday ......
# ..... saturday .....
# ...... sunday ......

print( ' pythonic '.center(50, '~') )
for day in days: print( f"{f' {day} ':.^20}" )
# ~~~~~~~~~~~~~~~~~~~~ pythonic ~~~~~~~~~~~~~~~~~~~~
# ...... monday ......
# ..... tuesday ......
# .... wednesday .....
# ..... thursday .....
# ...... friday ......
# ..... saturday .....
# ...... sunday ......

f-strings

# 3.8+
number = 14.3
print( f'{number=}' )
# 'number=14.3'

print( f'{ number  -  4  = }' )
# ' number  -  4  = 10.3'

from fractions import Fraction
one_third = Fraction(1, 3)
print( f'{one_third}' )
# '1/3'

print( f'{one_third = }' )
# 'one_third = Fraction(1, 3)'

string module

import string

string.ascii_lowercase
# 'abcdefghijklmnopqrstuvwxyz'

string.ascii_uppercase
# 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

string.ascii_letters          # a-z + A-Z
# 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'

string.digits
# '0123456789'

string.hexdigits
# '0123456789abcdefABCDEF'

string.punctuation
# '!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~'

cheatsheet

uppercase and lowercase

METHOD EXAMPLE RESULT
upper() 'py'.upper() 'PY'
lower() 'PY'.lower() 'py'
title() 'hello world'.title() 'Hello World'
capitalize() 'hello world'.capitalize() 'Hello world'
swapcase() 'Py'.swapcase() 'pY'
casefold() 'Straße'.casefold() 'strasse'(比 lower 更彻底，适合做忽略大小写的比较)

pad and fill

[!TIP]

>>> '-42'.zfill( 5 )
'-0042'
>>> f'{"-42":0>5}'
'00-42'
>>> f'{-42:05}'
'-0042'

references:

METHOD EXAMPLE F-STRING RESULT
s.center(w, c) 'py'.center(6, '*') f'{s:*^6}' '**py**'
s.center(w) 'py'.center(6, '-') f'{s:-^6}' '--py--'
s.ljust(w, c) 'py'.ljust(5, '.') f'{s:.<5}' 'py...'
s.ljust(w) 'py'.ljust(5) f'{s:<5}' 'py '
s.rjust(w, c) 'py'.rjust(5, '.') f'{s:.>5}' '...py'
s.rjust(w) 'py'.rjust(5) f'{s:>5}' ' py'
s.zfill(w) '42'.zfill(5) f'{n:05}' '00042'
s.zfill(w) '-42'.zfill(5) f'{-42:05}' '-0042'
- - f'{-42:0=6}' '-00042'(= 表示在符号和数字之间填充，只能用于数字)
s.expandtabs(n) 'a\tb'.expandtabs(4) - 'a b'

trim

METHOD EXAMPLE RESULT
strip(chars) ' py '.strip() 'py'
rstrip() 'xxpyxx'.rstrip('x') 'xxpy'
lstrip() 'xxpyxx'.lstrip('x') 'pyxx'
removeprefix(p) (3.9+) 'test_a'.removeprefix('test_') 'a'
removesuffix(s) (3.9+) 'a.py'.removesuffix('.py') 'a'

find

METHOD EXAMPLE RESULT
find(s) / rfind(s) 'hello'.find('l') 2 and -1 if not found
index(s) / rindex(s) 'hello'.index('z') ValueError if not found
count(s) 'hello'.count('l') 2
startswith(p) 'a.py'.startswith(('a', 'b')) True (可以传一个元组，匹配其中任意一个)
endswith(s) 'a.py'.endswith('.py') True
in 'ell' in 'hello' True

split and join

[!NOTE] | REPRESENTATION | DESCRIPTION | | -------------- | --------------------------- | | \n | Line Feed | | \r | Carriage Return | | \r\n | Carriage Return + Line Feed | | \v or \x0b | Line Tabulation | | \f or \x0c | Form Feed | | \x1c | File Separator | | \x1d | Group Separator | | \x1e | Record Separator | | \x85 | Next Line (C1 Control Code) | | \u2028 | Line Separator | | \u2029 | Paragraph Separator |

METHOD EXAMPLE RESULT
split(sep, n) 'a,b,c'.split(',') ['a', 'b', 'c']
split() ' a b '.split() ['a', 'b'] ( split by whitespace )
rsplit(sep, n) 'a.b.c'.rsplit('.', 1) ['a.b', 'c']
splitlines() 'a\nb'.splitlines() ['a', 'b']
partition(sep) 'k=v=x'.partition('=') ('k', '=', 'v=x')
rpartition(sep) 'a/b/c'.rpartition('/') ('a/b', '/', 'c')
join(iter) '-'.join(['a', 'b']) 'a-b'

replacement

METHOD EXAMPLE RESULT
replace(old, new, n) 'aaa'.replace('a', 'b', 2) 'bba'
translate(table) + str.maketrans() 'abc'.translate( str.maketrans('ab', 'xy') ) 'xyc'
format(...) '{}-{}'.format(1, 2) '1-2'
format_map(d) '{a}'.format_map({'a': 1}) '1'
encode(enc) '中'.encode('utf-8') b'\xe4\xb8\xad'

is-functions

METHOD RESULT
isdigit() / isdecimal() / isnumeric() 都是数字字符，三者的判定范围依次变宽
isalpha() 都是字母
isalnum() 都是字母或数字
isspace() 都是空白字符
isupper() / islower() 有字母，并且全是大写 / 全是小写
istitle() 是 title 格式，即每个单词首字母大写
isidentifier() 是合法的 Python 标识符
isascii() (3.7+) 都是 ASCII 字符
isprintable() 都是可打印字符
Copyright © marslo 2020-2026 all right reserved，powered by GitbookLast Modified: 2026-11-04 19:33:28

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