python - Limiting print output -

i have number of objects need print out terminal (for debugging). normal print function perfect, except objects large, print create millions of lines of output. i'd create function print does, except output truncated after predefined number of characters, replacing rest ....

what's way that?

note performance concern, ideally i'd prefer not save gigabyte-sized string , take first few characters it; similarly, pprint bit of problem since sorts keys in dictionaries (and millions of keys takes while).

example:

obj = [ [1, 2, 3], list(range(1000000)) ] my_print(obj, 20) # should output: # [[1, 2, 3], [0, 1, 2... 

python 3, if matters.

the reprlib module (python 3.x only) suggested @m0nhawk made purpose. here's how use it:

if you're fine default limits, can use reprlib.repr(obj):

import reprlib  obj = [[1, 2, 3], list(range(10000))]  print(reprlib.repr(obj)) 

output:

[[1, 2, 3], [0, 1, 2, 3, 4, 5, ...]] 

---

in order customize available limits, create reprlib.repr instance , set appropriate instance attributes:

r = reprlib.repr() r.maxlist = 4       # max elements displayed lists r.maxstring = 10    # max characters displayed strings  obj = [[1, 2, 3], list(range(10000)), 'looooooong string', 'a', 'b', 'c']  print(r.repr(obj)) 

output:

[[1, 2, 3], [0, 1, 2, 3, ...], 'lo...ing', 'a', ...] 

---

if you're dealing sequence objects refer themselves, can use repr.maxlevel limit recursion depth:

lst = [1, 2, 3] lst.append(lst)  # oh my!  r = reprlib.repr() r.maxlevel = 5   # max recursion depth  print(r.repr(lst)) 

output:

[1, 2, 3, [1, 2, 3, [1, 2, 3, [1, 2, 3, [1, 2, 3, [...]]]]]] 

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note reprlib.repr() returns string, doesn't print (unless you're in interactive console result of every expression enter gets evaluated , representation displayed).