Reading all stdin

Instead of having multiple calls to input, this can be very useful. Especially handy when parsing multiple lines

x=open(0).read()

Can be used with .split() and tuple unpacking too:

a,b,*m,e=map(int,open(0).read().split())

"Ternary" operator

Note that here both a and b would be evaluated.

x=a if c else b
x=[b,a][c]       # -5 chars

Interleave strings

Only really works for strings that are the same length

x=["hello","there","world"][c]
x="htweholerlrloed"[c::3]

Using input() to print final statement and exit

If the last thing you are doing in your program is print(x), it can be replaced with input(x). This will cause an IO Exception, nevertheless the output will still be printed before the program crashes. For most places this output is counted as valid.

A few reasons this would be helpful:

• If you already have a 2 input() calls, using I=input can save chars if you also use I() to print.
• It can be used to short-circuit:

if a:print(x)
else:print(y)

# becomes

if a:input(x)
input(y)        # if `a` is True, won't get here if there's no more in

Optimizing for loops

If the loops is simple and you don't actually care about the indices, you can do the following:

for i in range(5):_
for i in "."*5:_        # -3 chars
exec("_;"*5)            # -7 chars