scopes of local and global variable

[Pyenos]

#############################CODE##############################
t_len=0
class WORK:
def getwork(self):
def formattable(table_to_process,type):
TYPE=["p","t","T","s","i"] #list of types to format
if type==TYPE[1]:
def format_t():
row=[]
for col in table_to_process:

#######################
# ERROR PRONE PART #
#######################
if len(str(col))>t_len:
t_len=len(str(col))
#######################
# Error message says: #
# UnboundLocalError: local variable 't_len' referenced before assignment#

row+=col
if (table_to_process.index(col)+1)%7==0:
t_temp.append(row)
row=[]
format_t()
#################################################################

Interpreter says that t_len is local variable although i have
specified t_len=0 in line 1. Also, although i've stated t_len=0 in
line 1, it says that t_len is referenced before assignment.

 

[Fredrik Lundh]

#############################CODE##############################
t_len=0
class WORK:
def getwork(self):
def formattable(table_to_process,type):
TYPE=["p","t","T","s","i"] #list of types to format
if type==TYPE[1]:
def format_t():
row=[]
for col in table_to_process:

#######################
# ERROR PRONE PART #
#######################
if len(str(col))>t_len:
t_len=len(str(col))
#######################
# Error message says: #
# UnboundLocalError: local variable 't_len' referenced before assignment#

row+=col
if (table_to_process.index(col)+1)%7==0:
t_temp.append(row)
row=[]
format_t()
#################################################################
wow.

Interpreter says that t_len is local variable although i have
specified t_len=0 in line 1. Also, although i've stated t_len=0 in
line 1, it says that t_len is referenced before assignment.

each function introduces a new scope.

</f>

 

[Pyenos]

#############################CODE##############################
t_len=0
class WORK:
def getwork(self):
def formattable(table_to_process,type):
TYPE=["p","t","T","s","i"] #list of types to format
if type==TYPE[1]:
def format_t():
row=[]
for col in table_to_process:
#######################
# ERROR PRONE PART #
#######################
if len(str(col))>t_len:
t_len=len(str(col))
#######################
# Error message says: #
# UnboundLocalError: local variable 't_len' referenced before assignment#
row+=col
if (table_to_process.index(col)+1)%7==0:
t_temp.append(row)
row=[]
format_t()
#################################################################
wow.

Interpreter says that t_len is local variable although i have
specified t_len=0 in line 1. Also, although i've stated t_len=0 in
line 1, it says that t_len is referenced before assignment.

each function introduces a new scope.

</f>

does class WORK inherit t_len=0 from line1?

does def getwork() inherit t_len=0 from line1?

does def formattable(table_to_process,type) inherit t_len=0 from line1?

does def format_t() inherit t_len=0 from line1?

thanks.

 

[James Stroud]

Pyenos wrote:

#############################CODE##############################
t_len=0
class WORK:
def getwork(self):
def formattable(table_to_process,type):
TYPE=["p","t","T","s","i"] #list of types to format
if type==TYPE[1]:
def format_t():
row=[]
for col in table_to_process:
#######################
# ERROR PRONE PART #
#######################
if len(str(col))>t_len:
t_len=len(str(col))
#######################
# Error message says: #
# UnboundLocalError: local variable 't_len' referenced before assignment#
row+=col
if (table_to_process.index(col)+1)%7==0:
t_temp.append(row)
row=[]
format_t()
#################################################################
wow.


Interpreter says that t_len is local variable although i have
specified t_len=0 in line 1. Also, although i've stated t_len=0 in
line 1, it says that t_len is referenced before assignment.

each function introduces a new scope.

</f>

does class WORK inherit t_len=0 from line1?

does def getwork() inherit t_len=0 from line1?

does def formattable(table_to_process,type) inherit t_len=0 from line1?

does def format_t() inherit t_len=0 from line1?

thanks.

Yes and no, depending.

The rule of thumb I use is that if you assign in a function, the name is
not taken from the enclosing scope. For example, compare:

# example 1
def doit():
t_len = 42
def nested():
print t_len
nested()

doit() # will print 42


# example 2
def doit():
t_len = 42
def nested():
if t_len > 0:
print t_len
else:
t_len = 1
nested()

doit() # will get "referenced before assignment" error


You could make use of your WORK class here, depending on whether t_len
makes sense as a member of the WORK class:


class WORK:
t_len = 0
def getwork(self):
def formattable(table_to_process,type):
# etc., etc.
WORK.t_len = len(str(col))

James
--
James Stroud
UCLA-DOE Institute for Genomics and Proteomics
Box 951570
Los Angeles, CA 90095

http://www.jamesstroud.com/

 

[Pyenos]

#############################CODE##############################
t_len=0
class WORK:
def getwork(self):
def formattable(table_to_process,type):
TYPE=["p","t","T","s","i"] #list of types to format
if type==TYPE[1]:
def format_t():
row=[]
for col in table_to_process:
#######################
# ERROR PRONE PART #
#######################
if len(str(col))>t_len:
t_len=len(str(col))
#######################
# Error message says: #
# UnboundLocalError: local variable 't_len' referenced before assignment#
row+=col
if (table_to_process.index(col)+1)%7==0:
t_temp.append(row)
row=[]
format_t()
#################################################################

based on your advice i will try to answer my own questions:
no.

thank you kindly.

 

[Max Wilson]

does class WORK inherit t_len=0 from line1?

does def getwork() inherit t_len=0 from line1?

does def formattable(table_to_process,type) inherit t_len=0 from line1?

does def format_t() inherit t_len=0 from line1?

Not really, no. The global t_len is different than the local t_len--two
variables with the same name. You need to declare "global t_len" inside
your function so it knows that "t_len=..." is assigning to the old,
global variable instead of creating a new one.

See #6 here: http://zephyrfalcon.org/labs/python_pitfalls.html

-Max

 

[Pyenos]

Not really, no. The global t_len is different than the local t_len--two
variables with the same name. You need to declare "global t_len" inside
your function so it knows that "t_len=..." is assigning to the old,
global variable instead of creating a new one.

See #6 here: http://zephyrfalcon.org/labs/python_pitfalls.html

-Max

so, based on your advice, i think the answers are all no.

 

[Gabriel Genellina]

# Error message says: #
# UnboundLocalError: local variable 't_len' referenced before assignment#

See item 6 in "10 Python pitfalls":
<http://zephyrfalcon.org/labs/python_pitfalls.html>


--
Gabriel Genellina
Softlab SRL






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[Fredrik Lundh]

does class WORK inherit t_len=0 from line1?

does def getwork() inherit t_len=0 from line1?

does def formattable(table_to_process,type) inherit t_len=0 from line1?

does def format_t() inherit t_len=0 from line1?

you may want to read the documentation:

http://docs.python.org/ref/naming.html

</F>

 

[Fredrik Lundh]

does class WORK inherit t_len=0 from line1?

does def getwork() inherit t_len=0 from line1?

does def formattable(table_to_process,type) inherit t_len=0 from line1?

does def format_t() inherit t_len=0 from line1?

you may want to read the documentation:

http://docs.python.org/ref/naming.html

</F>