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Posts Tagged ‘pprint’
catch the output of pprint in a string
December 29, 2014
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Problem
If you have a large nested data structure (e.g. a list or dictionary), the pprint module is very useful to nicely format the output.
However, “pprint.pprint” prints directly to the stdout. What if you want to store the nicely formatted output in a string?
Solution
Use “pprint.pformat” instead.
Example:
>>> import pprint
>>> d = {"one": 1, "two": 2}
>>> pprint.pprint(d)
{'one': 1, 'two': 2}
>>> s = pprint.pformat(d)
>>> s
"{'one': 1, 'two': 2}"
Well, this is a small example, the real pretty formatting is not visible, but you get the point :)
Print in Python 2
October 1, 2010
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Let’s see some examples how to print to the standard output:
#!/usr/bin/env python
import sys
a = "Alice"
b = "Bob"
print a # "Alice\n", i.e. newline added
print b # "Bob\n"
print a, b # "Alice Bob\n", i.e. space is used as separator
print a + b # "AliceBob\n", i.e. the two strings are concatenated
for i in range(10):
print i, # "0 1 2 3 4 5 6 7 8 9", i.e. no newline, but space is still added
# notice the comma after i
print # "\n"
age = 7.5
print "Alice is " + str(age) + " years old." # must use str() for converting
# the float to string
print "%s is %.1f years old" % (a, age) # like C's printf()
for i in range(10):
sys.stdout.write(str(i)) # "0123456789", now you have full control
print
Using the pprint module, you can “pretty print” any data structure. It’s similar to PHP’s print_r function.
import pprint pp = pprint.PrettyPrinter(indent=4) li = [] # some complicated structure pp.pprint(li)
How to print to the standard error? Easy:
#!/usr/bin/env python
import sys
sys.stderr.write("Reactor meltdown! Leave the building immediately!\n")
Python Adventures 