29_common_beginner_python_errors.pdf
TRANSCRIPT
-
7/27/2019 29_common_beginner_Python_errors.pdf
1/1
My code isn't working :-(
Do you get anerror when yourun the code?
What type
of error do
you get?
Does the codeuse loops or ifstatements?
A list which should have
a value for every iterationonly has a single value
You have defined the listinside the loop: move it
outside
A loop which uses therange function misses
out the last valueThe range function isexclusive at the finish:
increase it by one.
I am trying to loop over a
collection of strings, butam getting individual
charactersYou are iterating over a
string by mistake
I am trying to writemultiple lines to a file butonly getting a single one
You have opened the fileinside the loop: move it
outside
A regular expression isnot matching when I
expect it toYou have forgotten to use
raw strings or escapebackslash characters
I'm trying to print a valuebut getting a weird-
looking string
You are printing an object(e.g. a FileObject) whenyou want the result of
calling a method on theobject
A number which shouldbe a fraction is comingout as zero in Python 2
You are dividing integersrather than floats.
Convert the numbers tofloats or from __future__
import division
I am reading a file but getting no inputYou have already read the contents of the file earlier
in the code, so the cursor is at the end.
A variable that shouldcontain a value does not
You are storing the return
value of a function whichchanges the variable
itself (e.g. sort)
Do you get anerror when yourun the code?
What type
of error do
you get?
Does the codeuse loops or ifstatements?
Two numbers which shouldbe equal are not
You are comparing a numberwith a string representationof a number (e.g. if 3 == "3")
A complex condition is notgiving the expected result
The order of precedence in the
condition is ambiguous - addsome parentheses
Do you get anerror when yourun the code?
What type
of error do
you get?
Does the codeuse loops or ifstatements?
Do you get anerror when yourun the code?
What type
of error do
you get?
Start here...
loops
neither
if
no
yes
also check...
IndentationError
SyntaxError
TypeError
NameError
AttributeError
IOError
KeyError
You've forgotten thequotes around a string
You have forgotten toput a colon at the end
of a def/if/for line
You have differentnumber of open andclose brackets in a
statement
You've called a method/function with the wrong
number or type ofarguments
You're trying to use anoperator on the wrong
type of objects
An object which youexpect to have a value is
actually None
You've used non-integernumbers in a list slice
You've used a mixture
of tabs and spacesYou haven't indented alllines in a block equally
You've misspelt a variable,function or method name
Your code calls a functionbefore it's defined
Your code uses avariable outside the
scope where it's defined
You've forgotten toimport a module
You've forgotten todefine a variable
You're trying to print asingle word and haveforgotten the quotes
You are calling amethod on the wrong
type of object
You're trying to open afile that doesn't exist
You're trying to look
up a key that doesn'texist in a dict
http://pythonforbiologists.com