Find characters that are similar glyphically in Unicode?

It is very unclear what you are asking to do here.

• There are characters whose canonical decompositions all start with the same base character: e, é, ê, ë, ē, ĕ, ė, ę, ě, ȅ, ȇ, ȩ, ḕ, ḗ, ḙ, ḛ, ḝ, ẹ, ẻ, ẽ, ế, ề, ể, ễ, ệ, e̳, … or s, ś, ŝ, ş, š, ș, ṡ, ṣ, ṥ, ṧ, ṩ, ….

• There are characters whose compatibility decompositions all include a particular character: ᵉ, ₑ, ℯ, ⅇ, ⒠, ⓔ, ㋍, ㋎, ｅ, … or s, ſ, ˢ, ẛ, ₨, ℁, ⒮, ⓢ, ㎧, ㎨, ㎮, ㎯, ㎰, ㎱, ㎲, ㎳, ㏛, ſt, st, ｓ, … or R, ᴿ, ₨, ℛ, ℜ, ℝ, Ⓡ, ㏚, Ｒ, ….

• There are characters that just happen to look alike in some fonts: ß and β and ϐ, or 3 and Ʒ and Ȝ and ȝ and ʒ and ӡ and ᴣ, or ɣ and ɤ and γ, or F and Ϝ and ϝ, or B and Β and В, or ∅ and ○ and 0 and O and ০ and ੦ and ౦ and ૦, or 1 and l and I and Ⅰ and ᛁ and | and ǀ and ∣, ….

• Characters that are the same case-insensitively, like s and S and ſ, or ss and Ss and SS and ß and ẞ, ….

• Characters that all have the same numeric value, like all these for the value 1: 1¹١۱߁१১੧૧୧௧౧౹౼೧൧๑໑༡၁႑፩១៱᠑᥇᧑᧚᪁᪑᭑᮱᱁᱑₁⅟ ① ⑴ ⒈ ⓵ ❶➀➊꘡꣑꤁꧑꩑꯱𐄇𐅂𐅘𐅙𐅚𐌠𐏑𐒡𐡘𐤖𐩀𐩽𐭘𐭸𐹠𒐕𒐞𒐬𒐴𒑏𒑘𝍠𝟏𝟙𝟣𝟭𝟷 🄂 Ⅰⅰꛦ㆒㈠㊀𑁒𑁧.

• Characters that all have the same primary collation strength, like all these that are the same as d: DdÐðĎďĐđ◌ͩᴰᵈᶞ◌ᷘ◌ᷙḊḋḌḍḎḏḐḑḒḓⅅⅆⅮⅾ Ⓓ ⓓ ꝹꝺＤｄ𝐃𝐝𝐷𝑑𝑫𝒅𝒟𝒹𝓓𝓭𝔇𝔡𝔻𝕕𝕯𝖉𝖣𝖽𝗗𝗱𝘋𝘥𝘿𝙙𝙳𝚍 🄳 🅓 🅳 🇩 . Note that some of those are not accessible through any kind of decomposition, but only through the DUCET/UCA values; for example, the fairly common ð or the newish ꝺ can be equated to d only through a primary UCA strength comparison; same with ƶ and z, ȼ and c, etc.

• Characters that are same in certain locales, like æ and ae, or ä and ae, or ä and aa, or MacKinley and McKinley, …. Note that locale can make a really big difference, since in some locales both c and ç are the same character while in others they are not; similarly for n and ñ, or a and á and ã, ….

Some of these can be handled. Some cannot. All require different approaches depending on different needs.

What is your real goal?

This won't work for all conditions, but one way to get rid of most accents is to convert the characters to their decomposed form, then throw away the combining accents:

# coding: utf8
import unicodedata as ud
s=u'U, Ù, Ú, Û, Ü, Ũ, Ū, Ŭ, Ů, Ű, Ų, Ư, Ǔ, Ǖ, Ǘ, Ǚ, Ǜ, Ụ, Ủ, Ứ, Ừ, Ử, Ữ, Ự'
print ud.normalize('NFD',s).encode('ascii','ignore')

Output

U, U, U, U, U, U, U, U, U, U, U, U, U, U, U, U, U, U, U, U, U, U, U, U

To find accent characters, use something like:

import unicodedata as ud
import string

def asc(unichr):
    return ud.normalize('NFD',unichr).encode('ascii','ignore')

U = u''.join(unichr(i) for i in xrange(65536))
for c in string.letters:
    print u''.join(u for u in U if asc(u) == c)

Output

aàáâãäåāăąǎǟǡǻȁȃȧḁạảấầẩẫậắằẳẵặ
bḃḅḇ
cçćĉċčḉ
dďḋḍḏḑḓ
eèéêëēĕėęěȅȇȩḕḗḙḛḝẹẻẽếềểễệ
fḟ
 :
etc.